The traditional outer boot, or shell of an Inline skate, has to be strong yet lightweight, robust yet forgiving providing for adequate ankle support without restricting movement. Good ventilation is a big advantage, especially on long skating sessions. Bearing many similarities to ski boots, all Inliners feature a hard outer shell for protection, with a separate removable soft inner boot designed for comfort. Boots are tightened around the skater's foot by a three-buckle system which ensures a firm and secure fit. Vented outer shells help keep the skater's feet at a comfortable temperature, and help avoid excessive moisture build-up which can lead to blistering.
Vents also help reduce the overall weight of the boot.
The separate inners incorporate breathable fabric and, in some models, high-tech memory foam, which effectively shapes itself to the skater's foot, resulting in a very comfortable fit. The separate inners can be removed from the outer boot following protracted periods of use and washed if necessary. For recreational skating, a large wheel diameter is generally preferred, as larger wheels have to make fewer revolutions than smaller diameter wheels to cover the same distance. This also means that larger diameter wheels demand less effort on the part of the skater. The quality of the urethane used in a wheel is measured by its rebound.