This Faithful Round Second Cut Engineers File is ideal for filing circular openings or concave surfaces and slightly tapered towards the point, with a double cut finish. For professional and frequent DIY use, fitted with a comfortable handle. Second Cut: approx. 36 teeth per 25mm (Medium). The FAIFIRSC12 engineers' file has the following specifications:Cut: round second. Blade Length: 300mm (12in). Blade Width: 10mm (3/8in).