Bath have announced the signing of Ireland international lock Ryan Caldwell with Harlequins' Lewis Stevenson set to move to join the province.
Caldwell, 25, has agreed a two-year deal and will move to the Recreation Ground from Ulster this summer.
He has made 79 appearances for Ulster and was capped twice during Ireland's tour to the USA and Canada in 2009. Bath rugby director Ian McGeechan said: 'Ryan will be a very good addition to the club.
'He has very good skills already, and he will develop these further as he matures. He is a big, powerful young lock, and so will create some real problems for the opposition.'
Caldwell follows another new second-row addition to the Bath squad, England international Dave Attwood, who has been recruited from Gloucester for next season.
Ulster have signed Stevenson as a replacement for Caldwell, who has been released a year early from his contract.
The 26-year-old, 6'7 lock will finish out the current season with Quins before joining up with Ulster.
Stevenson joins on a two-year deal. He has represented Ireland at Schools, Under-19 and Under-21 level and was previously on the books at Ulster before joining Exeter Chiefs.
His impressive form over a number of seasons culminated in him gaining selection for the National One League Team of the Season in 2009. This form alerted Harlequins who signed him that summer and he went on to make 29 appearances for the London outfit.
He joins a second row group that also includes Johann Muller, Dan Tuohy and Tim Barker.
He said: 'I’m very excited to be joining Ulster. When I left the province it was always my intention to come back with a bit of experience under my belt. It’s a great time for Ulster Rugby at the moment and it’s brilliant to be able to come on board. It’s going to be an exciting new challenge for me and I’m delighted.'
Ulster are in Magners League action against Llanelli Scarlets on Friday night and coach Brian McLaughlin has made five personnel changes to the starting line-up (kick off 19.05).
Ian Humphreys has shaken off a shoulder injury and is named at flyhalf despite leaving the field early against the Ospreys on Sunday. Andrew Trimble, Paddy Wallace and Tom Court go straight into the starting XV after being released from the Ireland squad.
Trimble takes up the right wing position with Craig Gilroy switching to the left and Simon Danielli dropping to the bench.
Prop Tom Court takes the place of Bryan Young who will also start from the bench. Paddy Wallace joins the in-form Nevin Spence in the centre, so Ian Whitten drops out of the match day squad.
The other notable inclusions are TJ Anderson in the back row in place of Willie Faloon and Andi Kyriacou at hooker instead of Nigel Brady.
Johann Muller will again captain the side in the continued absence of Rory Best, who is still on Ireland duty along with Stephen Ferris.
Ulster team to face the Scarlets at Stradey Park on Saturday, 19 February (7.05pm):
Ulster (15-9): A D’Arcy; A Trimble, N Spence, P Wallace, C Gilroy; I Humphreys, R Pienaar; (1-8): Tom Court, A Kyriacou, D Fitzpatrick, J Muller, T Barker, TJ Anderson, C Henry, P Wannenburg;
Replacements: N Brady, J Cronin, B Young, R Caldwell, R Diack, P Marshall, L Marshall, S Danielli.
