Stainless steel header bolts and spring washers for sk154 engines on many chinese 125cc motorcycles such as Herald classic 125 (euro 4) and other ybr based sk154 engines.
These are made of high quality srainless steel so wont rust like standard bolts, also the washers are spring washers so will not rattle loose.
We recommend applying a small amout of copper grease on the end of the thread when installing.