I am putting in my second collar order, now my dogs swim daily in saltwater and play hard against each other, male is 45kg and female is 31kg so they are tough dogs! Both collars are still ok after 2 years use, ordering new ones due to the great discount i was offered after submitting an order, not because the collars are not useable! Great web site and excellent customer service and products are tough and built for AMSTAFF or other tough breeds! Cheers Reece Australia