Guide bar 18″ .325 1.5mm 0.058″ fits 4500 (45cc), 5200 (52cc) and 5800 (58cc) Chinese chainsaws and also Plantiflex, BBT, B&Q, Silverline, Sanli, Whitemoss, Skatco, Eckman, Timbertech, Tarus and MT-9999 chainsaws. The guide bar is the steel rail that guides the saw chain around its cutting path the groove width (1.5mm/0.058″ gauge) and pitch (.325″) must match both the drive sprocket and the chain being used. Over time, the guide bar rails wear into a groove, the nose sprocket seizes or the oil feed hole blocks, causing the chain to run unevenly and produce rough, slow cuts. Replacing a worn guide bar restores smooth chain travel, reduces strain on the engine and maintains safe cutting performance.