Improved design high quality cast heads, featuring fully hardened and precision ground datum faces to resist wear. Protractor head and square head both incorporate spirit levels, allowing compound reading when setting jigs etc. Square Head - Square head with accurate machined faces, fixed angles of 45 and 90, built-in spirit level and adjusting nut. Centre Head - With fixed 90 angle, for finding the centre of round bar stock up to 120mm diameter 360 Protractor - Improved design features an offset arm for accurate readings, full scale graduations 0 - 180 - 0, and a centrally mounted spirit level vial for unrestricted viewing. 300mm/12" Rule - With deeply etched graduations on both sides or ease of reading and long life. Graduated in 0.5mm and 1/64" increments. Note: these are replacement/optional parts for use with the Oxford Full Scale Combination Set (OXD-330-3850K).