These split gears are used to reduce gear chatter & noise. However, when it comes to service & repair these split gears can often make disassembly & assembly of the drive train difficult. This tool is designed to clamp onto the gear & hold the 2 gear halves in alignment so making the assembly & disassembly easier. Tested & proven on Vauxhall 1.3 CDTi (B13) diesel camshafts & BMW B47 1.5 Diesel Balance shaft gears, this is a capable & reliable tool.