I had a mk3,sold about a month later,could not get on with it at all,the noise used to drive me mad i put tape over and it still drove me mad,like somebody said it sounds like a mobile phone.The collors used to slip off the ferrets,and yes they where on tight.The collors where a pain to get the batteries in,then they were hold there with two little plastic hooks,which sometimes used to pop out.I am back with the mk1 now where i should have stayed in the first place.