i run a ronstan 40 carbo block on the top. and a harken 40 carbo on the bottom, its plenty strong enough, but how ever it says on the harken that max line is 6mm, i use an 8mm rope but has some friction, take the rachet off and u will feel it run better, but i leave it on cos its a pain to change the switch over everytime as u have to undo the cleat from the block then put it on again