When i first for the mk3 locator and collar i dug to the collar that the ferret pulled off, it was a 5ft dig. did not want to loose it they are expensive! ever since i have had them on the ferrets tight and they seem to stay on. i put them on before i set off so when i get their if they are still on they are fine. good luck with your ferreting your doing a good job so far and in time you will learn more as you go along.