Toyota GR Yaris Racing H11 pro service cylinder head Stud, washer and nut set . This stud set helps to stop head lift when the power is increased on the engine with higher turbo boost pressure.
The Lamspeed studs can be replaced without removing the head as they have Allan key inserts in the end of the studs for fitting as long as you fit them one by one ( old one out new one in ) . They require to be tightened to 80ft lbs 

Any questions please ask