This watch band repair kit comes with different watch spring bars and a spring bar tool. Compatible with most of watch band or buckle. The spring bar's body and loading ends are made of 316L stainless steel . The internal spring is made of tempered 304 stainless steel. They are durable, strong and corrosion resistant. The size available in 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm both with 1.8mm body Diameter and 1.5mm body Diameter, and extra 2 different size watch spring bars as backup. The size you need is the same as the lug width of your watch case (or buckle width if the spring bar is to be used for a buckle).