The Toro 139-8250 Trimmer Bump Feed Head Assembly is a replacement cutting component that holds and dispenses trimmer line in compatible string trimmers. It uses a bump-feed mechanism that releases additional cutting line when the head is tapped against the ground during operation. This allows the operator to extend the line without manually opening the assembly. Replacing a worn or d... https://www.wholetoolbox.com/toro-139-8250-trimmer-bump-feed-head-assembly/139-8250.html