Dormer E500 straight flute taps are the only type of taps that can be used by hand, but they may also be used in a machine if required. Extremely versatile, can tap through or blind holes in most materials. When tapping blind holes straight flute taps should be used in sets. The three taps which form a set are known by more than one name. 1. Taper or First tap2. Second or Intermediate tap3. Bottoming, third or plug tap. Metric coarse straight flute taps. Tolerance: Class 2 for 6H FitSurface treatment: BrightMaterial: HSS High Speed SteelChamfer No: 1,2 and 3, Serial no 4 and 5Flute Geometry: Straight Flutes ISO529Size 20.0mm x 2.5 second