They're supposed to be tight. I believe they originally started as a safety device for bench competitions so you don't get crushed under the weight but its kinda morphed over time into an aid so you can bench more. It takes the weight off at the bottom of the stroke so you really have to train for lockout. Or at least thats how I understand it. I've never used one but I'd be interested just to see how it feels one day.

IronWorker