30 mm is about 1 1/4 inches. Quite common fuse availability in the states. The stock fuse holders in our SOHC4s take a 1 inch fuse, or 25 mm. A 30 mm fuse is too long. You can stuff one in there, but it doesn't make full contact with the fuse clips. This leads to them melting from added contact resistance.
You can get the proper length fuse if you shop a bit. Or, mail order from Mouser.
Cheers,