Universal Flex Core Sock Clamp-On Filter (U-401) by UNI Filter. Uni Universal Air Filters is where it all started over 40 years ago. Make a trick filter that clamps directly to the carburetor. For use on motorcycles go-karts tractors air compressors snowmobiles anything with a carburetor can benefit from a Uni. Completely washable for economical engine protection this filter allows for maximum air flow and dependability. Lets the filter bend for easy installation and movement.