Strange Spools are used in a wide variety of race cars to replace heavier and weaker cast-iron differential carriers. Spools permanently lock both axle shafts together so that both rear tires will always turn at the same speed. Strange Pro Race spools are forged with Strange designed tooling from premium steel. The forgings are machined on all critical surfaces by computer controlled machining centers and are fully heat treated. Super lightweight aluminum spools are ideal for applications where reduction of weight is essential (call to discuss application). Strange Pro Race steel spools are the lightest on the market and carry a lifetime warranty. Strange Standard Series spools share the same material characteristics as the lightweight pro race spools but without the lightening holes. Standard Series spools are an affordable and dependable option when weight is not a primary concern.