Welcome to Dr. Björn's Auto!
This is a large inline filter which traps particles from the tank for some time due to its size. As it is a clear filter you can also see if your tank has sediments and need cleaning. Approximately 1.5" diameter x 5" long - much larger than stock prefilters, and a great replacement for small prefilters as found on older Mercedes-Benz diesels! Also used in other SVO conversions on many other engines. The inlet and outlet fittings are stepped and can accept either 5/16" or 3/8" fuel hose (use a hose clamp!) The flow direction is indicated by an arrow molded into the plastic.