Nitro (NP1807-8.6) Aluminum Heavy Duty Girdle Cover for GM 8.6" Differential Made from 356 aircraft grade aluminum for durability and strength, then heat treated to T6 specifications and stress relieved Girdle covers are machined using a 3 step CNC process ensuring accuracy and quality, then each cover is inspected, de-burred and assembled by hand and packaged All Girdles incorporate a fill port and a drain port for ease of servicing and on average increase fluid capacity by approximately 1/2 pint, lowering the operating temperature of the differential by 15 degrees The average weight of a Nitro differential Girdle cover is about 7 pounds, larger covers will weigh more Made in the USA