The PVS-CB-58 three star black Buna-N static safe (10 - 10 ohmssq) non-marring straight probe (working temp. -5 to 250 F) is .63 in diameter. It is for use on all our vacuum tools with the exception of the Roto-Pic and PV-500.Specs amp; FeaturesProbeCupQuality: , Surface Resistivity : 10-10 ohmssq, Shape: Straight, Material: Black Buna-n, Tip Width: .63 (15.75mm) dia.