Westcott shatterproof rulers are made of K resin, also known as SBC. This is a premium grade plastic known for its exceptional clarity and impact toughness.
This is valid for the following parts:
13862 - Westcott 12" Shatterproof Ruler
45011 - Westcott 12" English and Metric Shatterproof Ruler, Clear
14381 - Westcott 12" Shatterproof Ruler, Assorted Translucent Colors
15989 - Westcott 6" Shatterproof Ruler