These labels are made of polyester: A highly durable synthetic film used primarily for outdoor applications involving high levels of abrasion or abuse. Polyester will stand up longer in a moist environment and is resistant to most oils and solvents. 

Sizes:  Large Oval - 5" x 3", Small Oval - 2-1/2" x 1-1/2" and Large Rectangular 8" x 2"