[pribusin]

But don't forget you have two widths of 4" per circle that you have to subtract to get the inner diameter (ID). If you draw a 42" OD circle that is 4" wide your ID is: 42"-(2x4")=34". That gives you a 4" wide band as a circle with an OD of 42". That is the white ring. The black ring would then be 34" OD and 26" ID. The innermost white circle would end up being 26" OD and 18" ID. Is my thinking wrong on this???

BTW, we posted on the USFIRST forum inquiring about the GE-10059 document. Hopefully that file will clear things up.