Bigger wheels roll faster but are harder to balance on, while smaller wheels are slower and more stable — so beginners usually start smaller and size up as they get confident. Wheel size also depends on your discipline — larger for speed & fitness, smaller for agility, slalom and skatepark.

Wheel hardness is the durometer — the “A” number. Higher (e.g. 100A) is harder: rolls faster but grips less and passes more buzz from the ground. Lower (e.g. 78A) is softer: more grip and a smoother ride, but it won’t roll as fast.