This stainless steel cap is tightened with a hex wrench, so you can even use it as a recessed head. [Features] Tightens with a hex wrench, so you can use it with an embedded head. Made of stainless steel, it has excellent corrosion and heat resistance. [How to use] Used for general tightening machines and vehicles, and for tightening that requires strength than hex bolts. However, it is not suitable for use in chlorinated environments such as near chlorinated environments or beaches.