Tap Adapter Size: #2. Shank Diameter (Decimal Inch): 20mm. Floating Function: Tension & Compression. FUNCTIONS AS IT SHOULD. NEW in original tube. NOT made in china. I have a number of different sizes and types of Tapping holders & quick change tap adapters. #1-#3 adapter sizes, English & metric, with & without clutch. If you need a different size please ask! Tension & compression Chuck.