I HAVE 2 MK1 BOXES AND 3 COLLORS , THEY WERE LAST USED LAST WINTER BUT MY SON NEVER TOOK THE BATTERIES OUT , HE HAS NOW PACKED UP WITH THE FERRETS AS HE HAS FOUND OUT WHAT GIRLS ARE ABOUT HA HA , I HAVE TRIED THEM AND THEY DONT WORK AS GOOD AS THEY SHOULD , THEY ONLY WORK AT ABOUT 3FT TO 4FT . ANY BODY WHOS KNOWS ABOUT COLLORS MITE BE ABLE TO SORT THEM OUT SO ANY OFFERS WITH POST