Most wheels are rated on a durometer scale - a rating of their relative hardness or softness. Outdoor wheels are softer and meant to roll smooth over uneven surfaces. The bigger outdoor wheels make for softer, smoother ride but will also be slower. The smaller outdoor wheels will have more agility but you will be able to feel more of the uneven surface under your feet. Check out our Wheel Recommendations page for more details on the best wheels for different surfaces and styles of skating.