Zinc Alloy Barbecue Knob The outer diameter is 38mm and the shaft size is 6.0mm; remember that the button holder is different, if you buy the wrong one, you will not be able to use it. Surface treatment: chrome plated, total height of knobs 2.4cm Hole orientation: +0 degrees, shaft insertion depth 1cm (0.4in) The shaft insertion depth is 1cm (0.4in); determine the location of the center shaft and the diameter of the center shaft before purchasing. If you don't know what to buy, you may not be able to use it.