The first set I had on added 12", the second set I put on was about 10" added. First set had 2 bunk casters and the bearings were garbage almost instantly so I exchanged for some sweet 8" poly casters from northern tool. The casters add about 10" overall. Makes rolling over surfaces a breeze. Got them from northern tool.
The 8" polys were 10 bucks each cheaper so I got a free weed burner out of the exchange