Question: what is the difference between #40 and #41 roller chain?
Answer: #41 Chain will only fit #41 sprockets, #40 sprockets are too wide. #420 will fit on #41 sprockets, its just a little bit heavier duty with a larger pin. #40 Chain will fit on #41 sprockets, it is basically the same as #420, except it has wider Rollers, it is considerably heavier duty than #41.