Suitable for nuts or bolts that are fitted with a flat washer on the bottom for pipe flanges, nuts for mechanical equipment (patent).
The SDSW-1 Series Technical Data.pdf

Plastic Protective Cover Cap for Hexagon Bolt Head:SDSW-1 |
Suitable for nuts or bolts that are fitted with a flat washer on the bottom for pipe flanges, nuts for mechanical equipment (patent).
The SDSW-1 Series Technical Data.pdf