The park tool bdt 2 belt drive tension gauge is a gono go style gauge designed to help set the proper tension on most belt drive systems and sizes also gauges rear cog parallelism and angularity park tool bdt 2 belt drive tension gauge features the bdt 1 isa gono go style gauge designed to help set the proper tension on most belt drive systems and sizes also gauges rear cog parallelism and angularity made in the usa and covered by park tool39s legend