For 5/16 inch No. 131A Yankee Spiral ratchet screwdrivers (Large). The Quick Chuck replaces a standard bit and then enables Snappy tools to be used. Dimensions: D=23 mm OD=68 mm SD=5/16 inch / 7.9 mm Shank Diameter: 5/16 Diameter Metric: 23 Overall Length Metric: 68