One of the best grips and also one of the most affordable. - Leapers UTG Ambidextrous Combat Foregrip, Symmetric Contour

This grip is perfect for pistol caliber carbines, AR-15 rifles, AK-47s, and I've even used one on an SKS with the TAPCO stock. There is no application I've found yet that this grip isn't perfect for. I've seen reviews that say it doesn't fit to their rails tightly, but I have purchased 4 of these and they fit every rail snugly. I actually had to tap the one on the AK rail with a mallet. One thing I will say is if you have smaller hands, this might be a little too fat for you. This is also a perfect foregip to compliment the Hogue beavertail and UTG beavertail AR grips. I do not store anything in any of these, but the bottom caps have never come off any of them in the field.