In reply to Mav359:
Even a lightweight locking krab is rated at about 25kN. That will hold 2500kg in a static hang. Your 85kg dog won't be a problem, and is unlikely to load you more than hanging under gravity. Unless your dog plans to go climbing, and experience long falls...
If you want a locking (screwgate or twist lock) krab, pop into your nearest Cotswold store or similar, and have a look. But, frankly, anything you buy off Amazon that is a decent size is likely to be more than strong enough; your grip on the lead may well be the limiting factor.
Post edited at 14:38