The General Tools 133ME 4" brass caliper is a handy tool for plumbers, electricians, jewelers and do-it-yourselfers for measuring rod diameters, plate thickness, and inside and outside of tubing. The 133ME features 4" outside and inside measuring capacity, is constructed of heavy gauge solid brass, has inside and outside graduations in 16ths and millimeters, has a close tolerance dovetail design with a smooth brushed finish with lacquer coating and finely stamped numbers and graduations.