This is a case to hold 15mm, 14mm, 13mm, 12mm, 11mm, 10mm, 9mm, 8mm, 7mm, and 6mm sockets. The case latches when you slide the socket holder into it, holding it securely. When you need to use one of the sockets you simple push the latching mechanism outward, which allows the socket holder to slide out. The same exact socket holder can also be used for: 5/8", 9/16", 1/2", 7/16", 3/8", 5/16", 9/32", 1/4", 7/32", 3/16" sockets. The sockets will fit very snuggly onto the holder until it wears in a little bit so be mindful of that.