The 51F is the smaller kit of the more popular 50F, perfect if you have minor repair than the full kit. REMA TIP TOP Vulcanizing Compounds are uniquely designed for cosmetic repair to tire and conveyor-belt surfaces (not for use where cord damage exists). When thoroughly mixed in equal portions, these materials chemically cure (at room temperature) producing a durable, permanent repair. Vulcanizing compounds are limited to bead repair of truck/OTR tires or sidewall repair of OTR tires only. CFC-free formula requires shorter drying times. REMA TIP TOP's Vulcanizing Compound has no equal when it comes to cold vulcanization injury filling. Equal quantities of A compound and B compound, thoroughly mixed, produce a durable permanent repair. This kit includes one 300 gram can of compound A, one 300 gram can of compound B and two 40 gram cans of Special Blue Cement.