HD Square Jack 12K Capacity Lifts 12-1/2"Strong, durable, and sturdy, the Bulldog 12,000 lb. support capacity square jack is the big reason why Bulldog has carried the load in agricultural, construction, heavy duty utility, and horse livestock trailer industries since 1923. All Bulldog 4" square jacks are rated for 12,000 lb. support capacity and 10,000 lb. lift capacity. The strength of the product, plus the wide variety of styles, makes this jack the best choice in its product class.