Our USA made custom 85A urethane 2.5" urethane coilover spring isolators are used in our coilover shock mount/bump stop kits and are designed to work with 1999-2005 NB Miata Shock Hats. They will NOT work with 1990-1997 NA Miata shock hats! They might also work with other shock hats, but we haven't tested them on anything besides the 1999-2005 Miata shock hats. The purpose of these is to center the coilover spring within the shock hat.
Designed to allow a 2.5" race spring to interface into a 99-05 Miata OEM shock hat. This is for the purpose of creating your own coilover kit using a Bilstein shock with our coilover sleeves/perches, and your choice of 2.5" race springs
85A "red" urethane offers a softer barrier between the spring and mount than our Spec Miata 95A urethane isolators and is the best choice for street/sport applications, but can also handle track and race use if preferred
For hardcore race and track applications, we recommend our 95A "black" isolators which offer a stiffer barrier between the spring and mount to maintain a more direct compliance and ultimate rigidity