Rex Quick Reference Guide for Durometers

DUROMETER TYPES	APPLICATIONS	INDENTOR SHAPE		MAIN SPRING
TYPE A (ASTM D2240)	Soft rubber, plastics, and elastomers, printer's rolls.		Flat Cone Point 35° Included Angle	822 GM 1.81 LB.
TYPE D (ASTM D2240)	Hard rubber and plastics such as thermo plastics, flooring and bowling balls.		Sharp Cone Point 30° Included Angle	4536 GM 10.0 LB.
TYPE B (ASTM D2240)	Harder elastomers and plastics. Paper and fibrous materials, Use above 93 Duro A.		Sharp Cone Point 30° Included Angle	822 GM 1.81 LB
TYPE C (ASTM D2240)	Medium hard elastomers and plastics. Also useful to avoid surface marks.		Flat Cone Point 35° Included Angle	4536 GM 10.0 LB
TYPE DO (ASTM D2240)	Dense granular material, textile windings.		3/32" Spherical	4536 GM 10.0 LB
TYPE O (ASTM D2240)	Very soft elastomers, textile windings, soft granular materials. Use below 20 Duro A.		3/32" Spherical	822 GM 1.81 LB
TYPE OO (ASTM D2240)	Light foams, sponge rubber gels, animal tissue.		3/32" Spherical	113 GM
TYPE OOO (NOT ASTM)	Ultra soft gels and sponge rubber.		1/2" Spherical	113 GM
TYPE M (ASTM D2240)	Materials as thin as .050"		Sharp Cone Point 30° Included Angle	--