Nylon washers are a must for a dependable antenna stud mount installation. If you have a non-Firestik stud mount there is a good chance that it has inferior ABS insulators. If so, we recommend that you upgrade it! ABS has a tendancy to crack, or worse, to compresses under pressure. If allowed to compress, the tension that holds your coupling nut together dimenishes and the coupling nut can come loose ... sometimes causing the loss of your antenna. Each package contains eight (8) pieces. All have a 3/4" (19mm) diameter and are made specifically for 1/2" holes and 3/8" bolts (industry standard sizes). The kit contains three washers with a 0.031" (1mm) shoulder, three with a 0.125" (3mm) shoulder and two with a 0.195" (5mm)shoulder.