The games get underway this evening.
A knee injury has ruled Bundee Aki out of Connacht's inter-pro derby with Ulster tomorrow.
The Lions centre will sit out the game at the Aviva Stadium in the United Rugby Championship but is still set to link up with the Ireland squad.
Tom Daly replaces Aki in Connacht's midfield with scrum-half Kieran Marmion and back-row Eoghan Masterson also in to start.
Ulster are boosted by the return of their captain Iain Henderson.
Fellow Ireland internationals Robert Baloucoune, Stuart McCloskey and Eric O'Sullivan also come in to start.
Conor Murray and Damien de Allende both get their first appearances of the campaign for Munster in their trip to Ospreys.
Tonight Leinster are away to Glasgow, where there's a 7.35pm start.

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