Brand: Parts Express. MPN: 240-2248. This classic plastic knob puts the perfect finishing touch on your guitar or other project. Also called hat or UFO knobs, these are commonly used on Strats and other guitars. Measures 1" base diameter x 0.5" height, with a "bell" taper to 0.63" at the face (26 x 12.7, 16 mm). For use with coarse splined shafts of 6 mm diameter, embossed indicator numbers.