I had my 1961 ZF's steering box's lower seal removed (pivot shaft, control arm). It measured about 41mm on my calipers. I say "about" because it was distorted a bit from the removal. I have purchased two seals that do not fit so far. The 40mm seal had the wrong o.d. but with an i.d. that is perfect. The o.d. just falls right in however. Too loose. Tried a 42.5 but is too big. The i.d. was too large as well. Anyone else had this problem who might have found a solution?