WIX Filter Mounting Base. Filtration is the foundation of an effective maintenance program, helping equipment remain closer to new condition for a longer period of time. Filtration is more than filters. WIX supplemental items include bases, connectors, installation aides, air filter wraps, bowls, supplemental additives, pressure gages and test kits. These items aid filter installation, extend useful service life, or provide data to assist in determining effective service life. Conversion Base to Convert 51750 Series Filters to 51749 Spin-on Filters; Inlet & Outlet Line thread sizes are 3/8-18 NPTF; stud size is 1 & 3/8-16.