I stock LPKs from RRA and also have a box with small sections where I keep about every small part for an AR, the lower parts especially. We sell a fair amount of LPK's and the profit margin on them are quite low, but what I think most shops dont get is that if a person knows your shop has small things they want, they will come in more frequently. While there, they will see whats new, maybe see something else they need or want. Most of the small parts like springs and detents, I just give away, it cost the shop maybe .30 or so. Just today, for example, a guy lost a detent spring and came in to get one. He asked how much and I told him dont worry about i. He was happy to have it and it didnt cost us much at all. He was about to walk out of the shop when he asked how much for that Vltor stock he saw while I was getting the spring, and bought it.