I cut these sleeves from a new piece of 12" DR 17 HDPE pipe from WL Plastics.

Inner Diameter
Inner Circumference
Wall Thickness
Outer Diameter
Sleeve Width
Weight
Hardness
Text		 11.25"
35.343"
0.75"
12.75"
6"
101 Ounces Each
60 Shore D
40 FT IPS 12" DR 17 WL Plastics SD PE4710 PE 445574C PC/PSI 125

The most accurate way to measure a tire is by circumference. Wrap a fabric measuring tape (typically used for sewing) around the outside of the tire. Measure the tire twice, deflated and inflated. See photo with two tire measurements, 34.4" deflated and 36" inflated. The inner circumference of these sleeves is 35.343" which is in between the two tire measurements (deflated & inflated).

Wider sleeves are more slippery (DM for 7" wide sleeves or bigger).
Skinny sleeves are more sticky.
Clean edges are better for racing and cornering.
Round edges are better for drifting and 360s.
PVC is harder and more slippery.
HDPE is softer and more sticky.

Sparky Sleeves are hand made by Scott Blake in Saint Paul, Minnesota.