Primary Chaincase Gasket, for use on BSA models: A7, A10, B31, B32, B33 & B34. O.E.M: 42-7507.Primary Chaincase Gasket: 42-7507. BSA A7, A10, B31 - B34. GAS 15SKU: 42-7507£4.55PriceQuantityAdd to Cart