Skate liner - The soft boot-like piece that fits inside the skate shell. Made in full and half sizes depending on the brand. This is the part of the skate that actually defines what size the skate is. Some skates may be a 10.5 skate but the difference is that the liner is a 10.5 and the shell is still a 10.
Fit System - Some skate liner have a fit system. Autofit is a basic fitting with basic contours, Customfit is a heat-moldable liner which fits to your foot a bit better, Memofit is a step above Autofit and remembers your foot pattern.
Skate Shell - The hard plastic piece which houses the skate liner. Usually only made in whole sizes no matter what brand.
Skate Skin - Only refers to TRS aggressive skates from Rollerblade. Often called an "Overboot", but is the same thing. Allows you to customize the look of your skates and also hides the hard shell.
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