The FLT series through-flow strainers are inserted into the central lubrication with progressive distributors to ensure sufficient purity of lubrication grease in the circuit (e.g. after topping up) and they protect PRA and PRB progressive distributors from contamination and make their service life longer. The strainers are inserted into the main pipe-line, in front of the first (master) distributor and then at the beginning of the ancillary branches of lubrication circuit. The strainers consist of the body and replaceable cleaning element.