Wheels are measured in 2 ways - the size and the hardness.
Smaller wheels are lighter and easier to maneuver, larger wheels are faster and more stable.
A higher durometer means a harder wheel (97-103a) slides more and is better for tricks. Lower durometer (78-87a) is softer and more suited for cruising.
Please note that Bones STF and SPF wheels use a "B" durometer scale and are all on the harder side, and 81-84b Bones wheels are similar to 99-103a durometer.
Have any questions, or need suggestions on anything? Send us an email at firstname.lastname@example.org we'd love to help you get rolling!