Small budget motorcycles may have a totally enclosed drive chain, but this is rare on larger motorcycles, an exception being the Norton rotary bikes. To prevent rapid wear of the chain and sprockets, it is customary to apply a greasy chain-lube via an aerosol. Many riders also fit aftermarket chain-oilers to feed a regular supply of oil to the chain at the rear sprocket. These chain oilers vary in sophistication, but all add significantly to the life of the chain. The custom of lubing by immersing the chain in a tin of hot grease ceased in the early 1970s, once most chains had rubber "O'-rings. The original Suzuki RE5 of 1975 came with a rear chain oiler, but the 1976 model had a sealed chain, and its oiler was deleted as "unnecessary".