Mazda supplied locking wheel nuts that will fit under the centre cap of original type 7 spoke alloy wheels & BBS wheels. Mazda part number T001-V3-860G cost around £15 (December 2008)
Mazda locking wheel nut set. There is no variation in the key from set to set so if you have this set on your car but have no key, ordering this set will enable you to remove your existing locking nuts. Part number is H001-86-260.
These may be available to order by mx5parts.co.uk or your local Mazda dealer.