I prefer the Eagle Stock Pack/cheek piece over the BlackHawk version, due to the material that contacts the face.
The "HawkTex" material (like Naugahyde) on the BlackHawk product has a sticky surface when damp, which can be quite uncomfortable in warm weather. It sticks to the face and yanks on the skin during recoil. The Eagle product has a different surface that is not stick and is much more comfortable to use.