Product Description For the really tough guys: the 1/8" Track Cog by Surly The track Cog is only made for really tough guys, who love the feeling of riding in pre-freehub times. It truly requires a lot of practice and some hardened leg muscles - but when you've got it dow, you have a lot of fun. Technical Information:Material:steel (SCM415 CroMoly)Compatibility:1.375" x 24 tpi ISO hubsTooth Count:13, 14, 15, 16, 17, 18, 19, 20, 21, 22Tooth Thickness:1/8"Thread Width:7.4 mmFeatures:Fixed Gear (without freehub) for Surly hubsuse only with lockringfor singlespeed chainsManufacturer Numbers:13 tooth:FW206114 tooth:FW206215 tooth:FW206316 tooth:FW206417 tooth:FW206518 tooth:FW206619 tooth:FW206720 tooth:FW206821 tooth:FW206922 tooth:FW2070 sold-outContents:1 x Surly Singlespeed Track Cog, 1/8"not incl. lockring Manufacturer: Surly 6400 W 105th St Bloomington MN 55438 USA derby@surlybikes.com Distributor: Cosmic Sports GmbH Leyher Straße 47 90763 Fürth Germany info@cosmicsports.de