To find the ideal roller skate size, it is safer to rely on the size guides provided by the brands. You should choose based on the measured foot size, if indicated, or the Mondo Point (MP) correspondence.

When trying them on, the feeling to look for is similar to that of other technical footwear, such as in winter sports. Once the skate is on and tightened, drop the skate, leg extended, on the rear wheel against the ground. This will help better position the foot inside the skate. When putting on the skate, you inevitably slide the foot forward, and it does not automatically move back, sometimes giving the false impression of being at the end of the skate.

Next, stand up: you should feel the tip of the liner in front of the toes, or even touch it, but without having the toes bent. Then move into flexion (shin/tongue pressure), which corresponds to the active position during skating: the foot moves slightly back towards the heel, and you should no longer feel the tip of the liner, or only barely touch it.

The liner relaxes and molds with use. It is natural to feel tight/secured in a new inline skate. This is the right feeling to maintain good support and not have your foot float inside the liner once it has adapted to your foot.

The frame is one of the most important parts to define the program of an inline skate according to the intended use.

Short frames (265 mm and less)
These are the frames that prioritize maneuverability and a lower center of gravity for balance, up to 4x84 mm. These are setups found in Freeride, Slalom inline skate ranges, and some Fitness skates. Perfect for easy movement, they do require more frequent pushing but are very dynamic from the start.

There are 3-wheel versions, with 100 mm or 110 mm wheels in a short setup. The advantage is to take advantage of the larger diameter for comfort, with less vibration on uneven surfaces, and for speed, which is better maintained thanks to the inertia of the 110 mm wheels, while remaining very maneuverable. However, the larger diameter means more height, which is not ideal for uses requiring precision (slalom, freeride) and a slightly less explosive start. You need to push a bit more at the start to "launch" the 100 or 110 mm wheels.

Medium frames (270 mm to 290 mm)
Medium frames provide more stability but are less maneuverable. They are found in mid-range and high-end fitness ranges, with wheels starting at 90 mm that offer more comfort compared to short frames. The longer the frame length, the closer you get to a touring/distance program, with longer 3x100 mm or 3x110 mm setups for more effective pushing over time, also proportionally improving comfort.

Long frames (290 mm and more)
Almost reserved for speed, with very long setups in 4x110 mm or 3x125 mm. Less maneuverable, which is less important on tracks, they require a bit more technique for the tightest turns. However, you get the best efficiency with every skate stroke, which is crucial when the goal is competitive! Whether in races against opponents or to surpass personal goals.