O RING SEALS
The O ring seals employed as the sealing method on the Aero Tank filler caps are to BS 1806 or BS4518 depending on the size. The material is fluorocarbon, commonly called Viton. This material is suitable for all fuels and lubricant, except Methanol, where nitrile seals should be specified for the main seal and centre pin seal. The suffix for the seal reference is changed from FPM75 to NBR70. The lock seal is nitrile in all cases.