hi my nephew is giving up on the mk1 locators and wants 2 swap his 2 mk1 boxes and 2 micro collars for a mk3 and collar both work ok and in good condition 1 has a 15ft dial on it but is an 8ft box and the sticker on the other is partly worn the 2 collars are velcro fastening but can easily be transfered to a normal 1 he lives nr manchester will post cheers DM