4″ Clear Filter. Becker External Clear Polycarbonate Canister Filter with Paper Element. An in line see through canister filter with paper filter element that removes 99% of particles down to 2 micron and connects easily on to the Becker Check Valve Assembly. Eliminates the need for removing the filter cover on the pump and allows for visual inspection of the filter element preventing any interruption in the vacuum process. Available with polyester element, call for information.