16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 28mm, 30mm. 1 Set (2 Tubes with 2 Screws). Over 25 Years. We are here to help and will try to resolve any issue you may have. Remove the end piece at the 12 o' clock position to locate the case/reference number and at the 6 o' clock position to locate the serial number.
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