Got a new mk3m colllar for xmas, used it once and think i prefer the original mk3 collar. Apart from nearly forgetting to switch it on, it went off while working once, took batteries out and put them back in and it was fine. dont no what caused it and it hadnt just switched off as it wouldnt switch back on. And aswell as that the old MK3 worked with hearing aid batteries (which i got for free). This one needs the propper 394 batteries. Only had the one outing with it so far and may come to prefer it with more use but first impressions make me prefer the original mk3 collar.