What the Heck is “Mondo”?
Mondo is a European sizing system that is determined by Centimeters, not random sizes like “8” or “10”. It is partially determined by the size of your feet and the size of your liners. If you have Mondo sized boots, the liners will be the same size. If you do not have Mondo sized boots, you will need to know this size.
To find your Mondo size, place your foot on a piece of paper and mark the longest toe and heel of your longest foot, or stand against a wall and mark the longest part of your foot on a piece of paper. 
Measure this distance in Centimeters (inches x 2.54). This is your Mondo size.
DO NOT CONVERT YOUR USA SIZE TO MONDO or VICE VERSA!!!! Use the steps we have listed above then upsize to the nearest whole size.
It will be one of the following sizes:
22
23
24
25
26
27
28
29
30
31
The size are from *.0 -*.9 If you measure a 26.7, let’s say, then you would go up to to a size 27 Upsizing is recommended for skiboarding because skiboarding requires a more upright stance which puts your toes slightly more forward than with traditional skiing.
When you first get your Thermo Flex liners and put them on your feet, they WILL BE UNCOMFORTABLE!!! This is because they are not molded to your foot, they are designed to some generic form. Also, they will be hard and will probably poke and prod your feet in places that feel strange to you. You must heat the liner to mold it to your foot – we suggest that you take this to a professional.
PLEASE SEE THE “SHELL TEST” FOR MORE INFO ON DETERMINING IF YOU’VE ORDERED THE RIGHT SIZE SHELL!!!!!!
The Thermofit liners are not designed only for ski boots. They can be used in many applications, such as snowmobiling, dog sledding, soft snowboard boots, hard snowboard boots, tele boots, ice climbing, snow shoeing, etc. – almost any boot than has a removable liner can take a Thermo Flex liner. If you want a warm, lightweight liner, this is the one for you!
Custom Fit
Lightweight in comparison to other liners
Much Warmer than conventional liners because it molds to your foot – no dead air spaces
Moldable up to 6 times
The liners need to be heated to form to your feet. We strongly suggest taking your liners and boots to a professional! This could be a ski shop, boot fitter, or anyone who has a special Thermo Flex liner oven. Reason: the oven is specially designed to only heat to a certain degree, and is timed so as to not over heat the liners. Also, there are certain other things that the professional will put on your foot in order to make your liners fit as best as possible. Usually, a ski shop will either not charge the customer or for a very nominal fee they will mold your liners for you. This is highly recommended.