For the first. It's superior to a free weight machine because it's safer for muscles and joints and can be used without a spotter.
Smooth operation is the key.
The Best Combination of Raw Power and Precision Design. This reduces friction resistance, consumes less energy and attains a far lower starting friction level than all other conventional bearings. It's superior to a free weight machine because it's safer for muscles and joints and can be used without a spotter. The Linear Bearing will handle heavy and consistent use with calm, even-handed durability. Simply lock the bar into position and add your weights.