Flange Conical Plug (EPDM) for M6 to M8 Screw Holes, (Ød2)4mm x (Ød1)10mm, 10mm Long, EPDM (Black), Pack of 100, HBJE100-B
SGD $16.20
These masking plugs have a flange to protect the surrounding area around the hole from treatment processes. You may also use them for holes with small counterbores if the dimensions fit.