I also bought a mrk3 this season had a mrk1 for years before that, i`ve just got the hang of it and i think it`s great on top of the fert everytime, the olny thing like everone is the collar the mrk1 collars where far better they shouldn`t have changed them, i had one slip a collar only once mind but one of my collars has a mind of it`s own sometimes works somethimes not! i`ll have to get it sent back