The move is in order to give them LV= Cup game time before the opener against England at Twickenham on 6 February.
The Ospreys have prop Adam Jones, wing Shane Williams and young backs Kristian Phillips and Tom Prydie available.
Scarlets hooker Matthew Rees, Blues duo Tom Shanklin and Sam Warburton, plus Sale's Eifion Lewis-Roberts and Rhys Gill of Saracens are also released.
Wales head coach Warren Gatland said: "There are a couple of players who have made recent returns from injury and are in need of game time, so for them it has been an easy decision to make.
"It doesn't get any bigger than a visit to Twickenham to start off a Six Nations campaign and we must make sure we get our preparation exactly right.
"That means some players remain in camp for the fortnight and there are others who will benefit from seeing some senior rugby action this weekend."