Synthetic, extended surface prefilter for reverse mount DuraMAX installations. Designed to prolong the lifecycle of the DuraMAX 4V final filter in reverse-mount installations. Reverse-mount installations, in which DuraMAX 4v final filters are installed with the "V's" as the air entry side, are common in inlet housings where limited space makes it difficult to install a separate bank of prefilters. Constructed with durable synthetic filter media formed into a cube configuration and fits snugly onto the air entry face of the DuraMAX 4v.