In addition to the Magpul stocks (except for the UBR which can't be installed on the 15-22), take a look into Vltor Imod stocks as well. I find them to incorporate a superior cheek weld to any of the Magpul varieties while having equal polymer quality and some storage space w/o breaking the bank too much (priced as much as the CTR).

And just to reiterate everyone else above, make sure it's spec'd for mil-spec buffer tubes.