It is the start of another big European weekend for the Irish provinces.

Leinster and Connacht will be the first into action.

Leinster say that close to 40,000 tickets have been sold ahead of their make-or-break European Champions Cup match-up against Harlequins.

After a narrow defeat at the Twickenham Stoop last Sunday, Leinster have to win tonight's Pool 2 clash in order to keep their qualification chances on-track.

Leinster head coach Matt O'Connor says that his side have spent this week focusing on cutting-out the mistakes that they made in London.

Also today in the Champions Cup, Munster's other two Pool 1 rivals, Saracens and Sale will clash from 5:15pm.

Ulster supporters will be keeping tabs on the other Pool 3 match this weekend as defending champions Toulon play host to the Leicester Tigers from 3:15pm.

Elsewhere, Glasgow face Toulouse in Pool 4 and both of this weekend's Pool 5 matches will be decided with Northampton at home to Treviso and Racing Metro taking-on the Ospreys in Paris.