Not a silly question at all, the larger ones were always 7/16AF and the smaller ones (like the rears on a mini) were 5/16AF.
Given changes in manufacture and perhaps more importantly the location of manufacturers they could well be Metric.
I use a ring or ring end of a combo whenever possible, soak in release oil the day before can save grief, they only need nipping up but some murder the things!
BR
Colin
