Genuine Honda W4 & W5 Quick Load line trimmer heads. Fits most straight shaft Line trimmer makes and models. ( Not just Honda) W4 = Small ( Ideally 25cc Line trimmers W5 = Large (Ideally 35cc and above Line trimmers ) These Quick Load heads allow you to easily and quickly replace the nylon line when you run out. Simply turn the head dial to match the arrow with the line hole and feed in your length of line, making sure both sides have an even length of nylon line, then simply rotate the Quick load head until you have the desired length ready for use. Everyone with a line trimmer should have a Honda Quick load head!