Checkline J-50 [J-50-E] Dial Thickness Gauge, 10m Range, 50mm Jaw Depth, Feeler E (5mm dia, curved) For Sheet Metal, Etc.. Resolution: 0.01 mm, Measuring range: 10 mm, Depth of jaw: 50 mm. Thickness gauges are used for measuring the thickness of leather, textile, cardboard, felt, rubber, sheet metal, foils, plywood, plastic parts of all kind, etc. The J-50 model is available with 5 different feelers, which can be found below. Measurement by manual pressure by plunger.