Why Do We Need Spare Tire Covers?- Long Term Sun Exposure Causes Small Cracks In Tires, Which Resulting In Air Leakage.- In Rainy Day, Corrosion Of Tire Rim By Acid Rain Will Affect The Appearance Of Vehicle And Cause Safety Hazards. Specification Selection Size 14 Inch Fits For Tire Diameter 60~69cm Size 15 Inch Fits For Tire Diameter 70~75cm Size 16 Inch Fits For Tire Diameter 76~79cm Size 17 Inch Fits For Tire Diameter 80~83cm How To Calculate Your Tire Diameter? Step 1: Find Your Tire Parameter. Itâ€s Written On Your Tire Side Step 2: Calculate Your Tire Diameter If Your Tire Is Written With P215/60r16, A=215 B=60 C=16. Tire Diameter=21.5*0.6*2+16*2.54=66.44 Cmyou Need To Buy The 14inch Cover. If Your Tire Is Written With P225/65r17.Tire Diameter=22.5*0.65*2+17*2.54=72.43 Cm.You Need To Buy The 15 Inch One.Exclusive Advantage:- Durable, Wash, Corrosion Resistance, Waterproof, Dust Proof, Sun Protection.-Adjustable Nylon Cord, Tighten The Adjustment Cord To Prevent The Tire Cover From Falling Off And Protect The Tire Tightly.