Proven Part Long Life String Trimmer Head for Stihl 27-2 Fits 4002-820-2304
4002-820-2310, also fits Stihl 25-2 trimmer head, so if you are running the 25-2 you can replace it with this long life 27-2

This complete trimmer head includes a metal cap on the spool. When you tap the head on the ground to disperse trimmer line, the metal cap protects the spool. This keeps the top of the spool from wearing out as quickly. 

Fits FS70R FS56R FS91R FS90R KM91R