Ospreys take on Toulouse, while Scarlets are at home to Exeter.
KO for both games is at 13:35
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Seven professional rugby players had to be rescued when they got stuck in a hotel lift - because they broke the weight limit.
Wales has fallen silent to mark the 50th anniversary of the Aberfan disaster, which cost the lives of 116 schoolchildren.
Philip Thomas was a 10-year-old pupil at Pantglas Junior School in Aberfan when a coal tip collapsed and slid downhill.