Magpul makes snap on cheek risers that go with the MOE and CTR line. Larue Tactical has a spring loaded reciprocating cheek riser that you can install on the MOE and CTR line without drilling holes, about $40. Reciprocating / sliding is so that even if the charging handle bumps into the cheek riser pad, it will scoot back out of the way and you can charge your rifle. If your stock is too collapsed with the cheek riser, it will interfere with charging. Some folks take a dremel and reduce the footprint of the cheek riser to suit what they need. I hear sometime this year they are making a budget version of the Magpul Precision Rifle Stock (aluminum) which is supposed to be half price, since it's polymer. the PRS is expensive but people say it's sturdy.