When I first brought my 52000 mile original 1978 Pinto home I soon discovered the rear seals leaked, along with a few other rubber-related items failing. I went about replacing everything questionable with so-far good success. However, I replaced my rear seals with 3214 units. Months later, when replacing the master cylinder and booster, I noticed my NEW seals leaking all over. Since the time I had done that job I learned that although the number 3214 (National, Federal Mogul, etc.) seal is indicated to be the proper replacement, IT IS NOT!! According to dimensions, the inner diameter is listed around 1.3 inches... the true axle diameter at the contact point is 1.25 in. I also discovered that the CORRECT seal is number 3199, with a correct, 1.25 Inner diameter. Please do not make my mistake... use the 3199 if you do not like doing a reseal after only weeks!! This info has probably already been submitted, but I figured a reminder would not hurt!

most likely a different material. Perhaps silicon instead of nitrile rubber.