Drop in T-nut is offer a fastening option that can be loaded from either from profile ends or side. Ridges on mating surface bite into the profile surface, creating a strong connection. Compatiable with 80/20: 3933, Works with 1515, 1530, 4040 and 4080 with 8mm slot. Please review specifications on listing prior to purchase. 100 pack / 1/4-20 Thread