Chassis: Also called the "frame". This is the plastic or metal part that houses the wheels and secures onto the skate boot. Often measured in millimeters. (i.e. 247mm)

Mounting bolts: The bolts that secure the frame/chassis onto the boot of the skate

UFS: This is a term used for skates that have a Universal Frame System built into them. A UFS skate will accept any UFS frame. By UFS standards, frame size only matters in perfomance and not in the actual fitting. For example, If you have a size 7 aggressive skate and the recommended size frame is a size 1, you can actually put a size 1 or 2 on the skate. They will both fit under the UFS standards, but the performance of the skate may suffer.