Wolf Tooth GCX XX1 Replacement Cog 44T BlackWolf Tooth GCX XX1 Replacement Cog 44T Black. GCX cogs replace the largest cog on SRAM 11 speed XD cassettes for extra durability and to lengthen the cassettes life. GCX cogs replace the largest cog on SRAM 11 speed XD cassettes for extra durability and to lengthen the cassettes life; also offered in a 44T for expanded climbing range Not compatible with any other cassettes TECH SPECS Defined Color Black Tooth Count 44 Intended Cassette Compatibility