We look at all the Round 18 matches
With just five rounds left to decide which teams will contest the play-offs, there is a new leader of the Pro12 with Glasgow Warriors taking over the mantle from Ulster.
For the fourth round in succession, Ospreys swapped places with Scarlets in the play-off Zone.
Three of those teams are in action on Friday; Ulster traveling to Edinburgh, Ospreys hosting Welsh rivals Newport Gwent Dragons, and Scarlets in Italy to face Zebre.
Edinburgh can do their Scottish neighbours, Warriors, a favour if they can defeat Ulster however their record against the Ulstermen is not great.
Meanwhile Ospreys and Scarlets must both be looking to come away with maximum points from opponents who are sitting at the wrong end of the table in their bids to reach the play-offs.
The leaders, Glasgow Warriors, are not in action until Saturday, and are the only one of the potential play-off teams to face another side from the top half of the table when the visit Leinster at the RDS.
Munster will also be looking for maximum points in the all-Irish clash against Connacht if they are to make a final push for the knockout stages.
With just two points separating the top three teams in the table, whilst it is even closer for the final play-off spot, there is
definitely all to play for still as the Pro12 enters its closing stages.
We look at all the Round 18 matches!
Friday, March 22
Zebre v Scarlets
(Stadio XXV Aprile - Kick-off: 19.00; 18.00 GMT)
Zebre have lost all 23 matches they have played this season in all competitions, eight by seven points or less.
Scarlets only defeat in the last four rounds of Pro12 play was 5-32 to Leinster in Dublin on 23 February.
The Scarlets have lost their last five away games in all tournaments since beating Cardiff Blues 9-6 at the Arms Park in the Pro12 on 21 December.
The Welshmen have already been defeated in Italy this season, going down 20-22 at Treviso on 29 September.
Scarlets won 22-13 when the two sides met in round 8 of this season's Pro12.
Zebre: 15 Alberto Bennettin, 14 Leonardo Sarto, 13 Matteo Pratichetti, 12 Giovanbattista Venditti, 11 Sinoti Sinoti, 10 Paolo Buso, 9 Alberto Chillon, 8 Andries Van Schalkwyk, 7 Mauro Bergamasco, 6 Emiliano Caffini, 5 Josh Sole, 4 Quintin Geldenhuys (captain), 3 David Ryan, 2 Carlo Festuccia, 1 Matias Aguero.
Replacements: 16 Andrea Manici, 17 Andrea De Marchi, 18 Luciano Leibson, 19 Michael Van Vuuren, 20 Filippo Cristiano, 21 Tito Tebaldi, 22 Luciano Orquera, 23 Roberto Quartaroli.
Scarlets: 15 Gareth Owen, 14 Liam Williams, 13 Gareth Maule, 12 Adam Warren, 11 Andy Fenby, 10 Owen Williams, 9 Aled Davies, 8 Rob McCusker (captain) 7 Johnathan Edwards, 6 Aaron Shingler, 5 Johan Snyman, 4 George Earle, 3 Deacon Manu, 2 Matthew Rees, 1 Phil John.
Replacements: 16 Emyr Phillips, 17 Rhodri Jones, 18 Jacobie Adriaanse, 19 Jake Ball, 20 Sione Timani, 21 Rhodri Williams, 22 Aled Thomas, 23 Scott Williams.
Referee: Peter Fitzgibbon (Ireland)
Assistant Referees: Stefano Pennè, Stefano Roscini (both France)
TMO: Carlo Damasco (France)
Ospreys v Newport Gwent Dragons
(Liberty Stadium - Kick-off: 19.05; 19.05 GMT)
Ospreys have won just one of their last three Pro12 encounters: 24-7 at home to Edinburgh in round 16.
The Welshmen have won their last seven Pro12 contests at Liberty Stadium since Glasgow won there, 28-10, on 14 September.
Ospreys have not lost a Pro12 game to a fellow Welsh region since they visited Newport on 6 January 2012, and slipped up 20-21.
Newport Gwent Dragons' last three games in the tournament have strangely all been won by the away side! Dragons have won their last two away matches in all competitions but have not won three in a row on the road since October 2004.
The Men from Gwent have lost their last five Pro12 encounters against fellow Welsh regions.
The two sides have already met twice at Rodney Parade this season with Ospreys winning 14-3 in the Pro12 on New Year's Eve and Dragons taking the Anglo-Welsh Cup tie 18-14 on 26 January. Dragons' only previous victory at Liberty Stadium was 21-16 on 30 October 2010.
Ospreys: 15 Richard Fussell, 14 Tom Habberfield, 13 Jonathan Spratt, 12 Ashley Beck, 11 Tom Isaacs, 10 Dan Biggar, 9 Kahn Fotuali'i, 8 Jonathan Thomas, 7 Justin Tipuric, 6 James King, 5 Ian Evans, 4 Alun Wyn Jones (captain), 3 Adam Jones, 2 Richard Hibbard, 1 Ryan Bevington.
Replacements: 16 Scott Baldwin, 17 Duncan Jones, 18 Dmitri Arhip, 19 Lloyd Peers, 20 George Stowers, 21 Rhys Webb, 22 Matthew Morgan, 23 Ben John.
Newport Gwent Dragons: 15 Dan Evans, 14 Adam Hughes, 13 Pat Leach, 12 Jack Dixon, 11 Ross Wardle, 10 Steffan Jones, 9 Wayne Evans; 8 Lewis Evans (captain), 7 Nic Cudd, 6 Dan Lydiate, 5 Adam Jones, 4 Andrew Coombs, 3 Nathan Buck, 2 Sam Parry, 1 Owen Evans.
Replacements: 16 Hugh Gustafson, 17 Phil Price, 18 Dan Way, 19 Ian Nimmo, 20 Toby Faletau, 21 Jonathan Evans, 22 Will Harries, 23 Hallam Amos.
Referee: John Lacey (Ireland)
Assistant Referees: Ian Davies, Wayne Davies (both Wales)
TMO: Gareth Simmonds (Wales)
Edinburgh v Ulster
(Murrayfield - Kick-off: 19.30; 19.30 GMT)
Edinburgh have lost their last eleven contests in all competitions since their 24-23 victory over Connacht at the Sportsground in the Pro12 on 1 December - that win represents their only one over an Irish province since
Edinburgh's sole win at Murrayfield since September was against Scarlets, 23-13, on 23 November.
Ulster's 29-all draw last time out against Treviso saw them drop off the top of the Pro12 table for the first time since
The Ulstermen's recent form has seen them gain just 14 points from a possible 30 over their last six matches in the competition.
Edinburgh have won just one of their last eight fixtures with Ulster in all competitions since 2009: 21-16 at Murrayfield in the Pro12 on 22 October 2010.
Edinburgh: 15 Greig Tonks, 14 Lee Jones, 13 Dougie Fife, 12 Ben Atiga, 11 Tom Brown, 10 Piers Francis, 9 Sean Kennedy, 8 Netani Talei, 7 Ross Rennie, 6 Stuart McInally, 5 Sean Cox (captain), 4 Grant Gilchrist, 3 Willem Nel, 2 Steven Lawrie, 1 Allan Jacobsen.
Replacements: 16 Ross Ford, 17 John Yapp, 18 Geoff Cross, 19 Perry Parker, 20 Hamish Watson, 21 Richie Rees, 22 Harry Leonard, 23 Tim Visser.
Ulster: 15 Jared Payne, 14 Andrew Trimble, 13 Darren Cave, 12 Stuart Olding, 11 Michael Allen, 10 Paddy Jackson, 9 Paul Marshall, 8 Robbie Diack, 7 Mike McComish, 6 Dan Tuohy, 5 Lewis Stevenson, 4 Johann Muller (captain), 3 John Afoa, 2 Rob Herring, 1 Tom Court.
Replacements: 16 Niall Annett, 17 Calum Black, 18 Ricky Lutton, 19 Nick Williams, 20 Ali Birch, 21 Michael Heaney, 22 Ricky Andrew, 23 Peter Nelson.
Referee: Leighton Hodges (Wales)
Assistant Referees: David Changleng, Graeme Marshall (both Scotland)
Saturday, March 23
Munster v Connacht
(Musgrave Park - Kick-off: 17.45; 17.45 GMT)
Munster are without a win in their last three Pro12 fixtures since beating Edinburgh 30-3 in Cork on 9 February.
That victory ended an unwanted run of two successive defeats at Musgrave Park to Scarlets and Cardiff Blues.
The Munstermen have not welcomed a fellow Irish province to Musgrave Park since Ulster were the visitors in March 2008 and were repelled 42-6.
Connacht have won four of their last five Pro12 games including victories in their last three matches against Ospreys, Blues and Zebre.
Connacht have only once before won four in a row in the tournament – in September 2002. Connacht's only away win in the competition against a fellow Irish province came when they visited Donnybrook in September 2002 and beat Leinster 26-23.
Munster's only previous defeat to Connacht in this tournament was 6-12 at the Sportsground on 28 December 2008.
Connacht have not won on Munster soil since a trip to Thomond Park in the Interprovincial Championship in November 1986.
Munster: 15 Felix Jones; 14 Doug Howlett, 13 Casey Laulala, 12 James Downey, 11 Doug Hurley, 10 Ronan O'Gara, 9 Cathal Sheridan, 8 James Coughlan, 7 Sean Dougall, 6 Tommy O'Donnell, 5 Paul O'Connell, 4 Donncha O'Callaghan, 3 Stephen Archer, 2 Damien Varley, 1 David Kilcoyne.
Replacements: 16 Mike Sherry, 17 Wian du Preez, 18 BJ Botha, 19 Billy Holland, 20 Niall Ronan, 21 Duncan Williams, 22 Ian Keatley, 23 Ivan Dineen.
Connacht: 15 Robbie Henshaw, 14 Danie Poolman, 13 Eoin Griffin, 12 Dave McSharry, 11 Gavin Duffy (captain), 10 Dan Parks, 9 Kieran Marmion, 8 John Muldoon, 7 Willie Faloon, 6 Andrew Browne, 5 George Naoupu, 4 Mick Kearney, 3 Nathan White, 2 Jason Harris-Wright, 1 Brett Wilkinson.
Replacements: 16 Adrian Flavin, 17 Denis Buckley, 18 Ronan Loughney, 19 Mike McCarthy, 20 Eoin McKeon, 21 Paul O'Donohoe, 22 Miah Nikora, 23 Fetu'u Vainikolo.
Referee: Alain Rolland (Ireland, 56th competition game)
Assistant Referees: Michael Black, Brian MacNeice (both Ireland)
Benetton Treviso v Cardiff Blues
(Stadio Monigo - Kick-off: 19.30; 18.30 GMT)
Benetton Treviso are unbeaten in their last two Pro12 fixtures, winning against Munster 34-10 at Stadio Monigo and drawing 29-all with Ulster at Ravenhill.
Treviso's only defeat in their last five home games in all competitions was 13-14 to Leicester in the European Cup on 15 December.
Cardiff Blues' only win in their last four Pro12 matches was 17-16 over Edinburgh at Murrayfield in round 15.
The Blues have won all 15 previous contests they have played against Italian opponents in all competitions.
The two sides have met on five previous occasions with Blues taking five wins and Treviso gaining just one losing bonus point for a 13-20 defeat at Stadio Monigo in the Pro12 on 3 March 2012.
Treviso: 15 Brendan Williams, 14 Ludovico Nitoglia, 13 Tommaso Iannone, 12 Doppies La Grange, 11 Christian Loamanu, 10 Alberto Di Bernardo, 9 Fabio Semenzato, 8 Manoa Vosawai, 7 Alessandro Zanni, 6 Dean Budd, 5 Corniel Van Zyl , 4 Francesco Minto, 3 Lorenzo Cittadini, 2 Leonardo Ghiraldini (captain), 1 Alberto De Marchi.
Replacements: 16 Giovanni Maistri, 17 Michele Rizzo, 18 Jacobus Roux, 19 Antonio Pavanello, 20 Paul Derbyshire, 21 Simone Favaro,, 22 Edoardo Gori, 23 James Ambrosini.
Cardiff Blues: 15 Jason Tovey, 14 Owen Williams, 13 Gavin Evans, 12 Dafydd Hewitt ,11 Chris Czekaj, 10 Ceri Sweeney, 9 Lloyd Williams, 8 Luke Hamilton, 7 Rory Watts-Jones, 6 Michael Paterson, 5 James Down, 4 Filo Paulo , 3 Benoit Bourrust, 2 Kristian Dacey, 1 Taufa'ao Filise.
Replacements: 16 Marc Breeze, 17 Sam Hobbs, 18 Scott Andrews, 19 Lou Reed, 20 Thomas Young, 21 Robin Copeland, 22 Lewis Jones, 23 Gareth Davies.
Referee: Giuseppe Vivarini (France)
Assistant Referees: Claudio Passacantando, Simone Boaretto (both France)
TMO: Mauro Dordolo (France)
Leinster v Glasgow Warriors
(RDS Dublin - Kick-off: 19.45; 19.45 GMT)
The Pro12's top two teams on current form meet head on at the RDS, with Glasgow having dropped just one possible league point and Leinster only two over the past six rounds.
Leinster remain the only side left in the Pro12 with a 100 percent home winning record in the competition this season.
The Leinstermen's most recent defeat was 19-27 to Ulster at Ravenhill on 21 December.
Glasgow Warriors top the table in the Pro12 courtesy of a record run of seven straight victories in the tournament, since they lost 3-31 at Munster on 1 December.
Warriors have picked up maximum points in each of their last five matches.
Glasgow have not beaten Leinster in any competition since their 23-19 win at the RDS in the Pro12 on 17 September 2011.
Leinster: 15 Isa Nacewa, 14 Dave Kearney, 13 Eoin O'Malley, 12 Gordon D'Arcy, 11 Andrew Conway, 10 Ian Madigan, 9 Issac Boss, 8 Jordi Murphy, 7 Shane Jennings, 6 Kevin McLaughlin, 5 Quinn Roux 4 Leo Cullen (captain), 3 Michael Bent, 2 Sean Cronin, 1 Heinke van der Merwe.
Replacements: 16 Aaron Dundon, 17 Jack McGrath, 18 Jamie Hagan, 19 Devin Toner, 20 Dominic Ryan, 21 John Cooney, 22 Brendan Macken, 23 Fionn Carr.
Glasgow: 15 Peter Murchie, 14 Tommy Seymour, 13 Alex Dunbar, 12 Peter Horne, 11 DTH van der Merwe, 10 Duncan Weir, 9 Niko Matawalu, 8 Josh Strauss, 7 John Barclay, 6 Robert Harley, 5 Alastair Kellock, 4 Tom Ryder, 3 Ed Kalman, 2 Dougie Hall, 1 Moray Low.
Replacements: 16 Pat MacArthur, 17 Gordon Reid, 18 Jon Welsh, 19 James Eddie, 20 Ryan Wilson, 21 Henry Pyrgos, 22 Ruaridh Jackson, 23 Sean Lamont.
Referee: Nigel Owens (Wales)
Assistant Referees: Leo Colgan, B O'Connell (both Ireland)
TMO: Dermot Moloney (IFRU)