Product Description The 25 mm B-screw for Wolf Tooth Components GC with Shimano rear derailleur The 25 mm long B-screw by Wolf Tooth Components must be used if the Wolf Tooth GC 42-tooth sprocket is used with a Shimano rear derailleur. It may also be required for the GC 40-tooth sprocket. Only if you combine the GCs with the GoatLink rear derailleur adapter, this longer B bolt is not necessary. It is made of high-quality stainless steel and has an M4 thread. Technical Information:Material:stainless steel (18-8)Size:M4 x 25 mmCompatibility:Wolf Tooth GC 40 for Shimano 10-speedWolf Tooth GC 42 for Shimano 10-speedManufacturer Number:BSCREW25 Contents:1 x Wolf Tooth Components 25 mm B-screw Weight: silver: 2.5 g Manufacturer: Wolf Tooth Components 6400 W 105th St Bloomington MN 55438 USA info@wolftoothcomponents.com Distributor: Cosmic Sports GmbH Leyher Straße 47 90763 Fürth Germany info@cosmicsports.de