The Toro 139-8250 Trimmer Bump Feed Head Assembly helps advance and manage cutting line on compatible string trimmers during operation. Designed as a replacement bump feed head assembly, it uses the bump-feed mechanism to release additional line when the head is tapped against the ground, helping maintain the desired cutting length. A properly functioning head can support consistent t... https://www.wholetoolbox.com/toro-139-8250-trimmer-bump-feed-head-assembly/139-8250.html