Correct on the purpose of the extension. The rim bolts on mine are English but much or the tractor is metric so you better buy a set with both. The owners manual gives values for both unified inch and metric but I see no table of what is used where.Thanks for advice. Let me clarify: the 12 inch extension is to accommodate the inset dish and allow force to be applied perpindicular to wrench so you don't try to round off nut head. Also are the nuts metric or English ?