Genuine Stihl hexagonal head screw for disc cutters. the part number of this screw is 4201 708 8401. 
we are selling this as a group of 3 screws which are used to fit the pulley guard that supports the movement of the main cutting blade.
this is suitbale for the following models of Stihl disc cutters. 

TS 350
TS 350 AVE
TS 360
TS 400
TS 460
TS 510
TS 760

each screw retails at £1.36+VAT, or £1.63, which would be £4.90 inclusive of VAT for all 3