BSA Speedometer Drive Bush Sealing O-Ring. If your BSA is leaking or Dripping oil from your Speedometer Drive, chances are your Seal is old and is in need of replacement! This Thick O-Ring is an excellent quality replacement part that fits! Just install and away you go! Fits early BSA 500 & 650 Twins (Star Twin, Thunderbolt, etc) from 1962-1963 that feature the Speedometer Drive under the Transmission. Please refer to your parts catalog for proper fitment.*****Please note that this Set may fit other BSA Unit models that are not listed abouve!*****Made in EnglandO.E.M Part number is 65-3395