Adapter comes in a kit bundled with the following items: (a total value of $12.95). A Free stainless steel buckle. B Pair of 1.3 and 1.5 stainless steel bars C. Spring bar/buckle replacement tool. Adapter is made of stainless steel and fitted with a 1.8mm diameter stainless steel seamless double flange spring bars. It is designed to fit 42mm Apple watch. 42mm adapter is made to fit 24mm straight end watch bands. Installation: (Use the supplied kit for installation)1. Connect the replacement band with the same color buckle as adapter. 2. Since the spring attached on adapter is 1.8mm, on the thinner watch band you may need to use 1.3mm or 1.5mm spring bars from the kit. 3. Slide band on watch groove with 3 black rubber pieces side up