I need to buy a chrome headlight rim for my M20 but am unsure which size rim to order. Is the measurement for the rim taken at the rear where the larger diameter is or at the front of the rim where the smaller diameter is? Cheers Neil.

If you follow the pre-war Lucas system then the measurement was taken at the rear, but who knows what a modern seller might be doing.

Lucas referred to the DU42 as 7" front with 6" aperture and listed the rim as 7" with the glass sized at 6 19/32"

Is the shell marked with a type / model number ? There are several different forms of clip / screw fixing also.

Is it a civvy or a WD bike?....What year?....Ian

email (option): ian@wright52.plus.com