This is a high quality made in Italy Tecomec (230mm - 10") Universal Pro-Trim head. The Tecomec Pro-Trim flail blade system creates less resistance (load) then most nylon line trimmer heads, developing higher rpm for superior cutting performance with most gas-powered trimmers. The tough Pro-Trim cutting blades have extremely durable beveled edges for long life. Made of high-impact nylon, they withstand heavy-duty operation in the toughest cutting conditions. These double-edge blades are supported by metal bushings and retract fully upon impact with a solid object, preventing damage to the blades and structures. This pro-trim head is recommended for trimmers up to 33cc. This Fixed-Line head features a centering bore for both 20mm and 1" (25.4mm) arbor shafts. The head is shipped with adapter ring and a washer kit, you do need to use the OEM nut/ bolt/fastener from the trimmer you are installing this on to adapt this head on your machine. Tecomec is an Italian company and they are a world leader in producing Chainsaw, Brushcutter and Trimmer Accessories. Please visit their web site at Tecomec.com to learn more about this company that since 1985 has been selling great product all over the world!