Silca Pista/SuperPista rebuild Nut/Washer Kit. If you are rebuilding your older SILCA Pista or SuperPista pump with a new leather washer, you might consider also using this updated washer and nut kit. Reusing the original nylon inserted nut can lead to later loosening of the assembly as the nylon insert will take a set over time. A new bolt kit guarantees years and years of trouble-free service. This kit uses only nuts and washers from a factory in Ohio which we chose for their class-leading environmental policies and ultra-low energy galvanizing processes.