Cage calls this: silicone sponge rubber (low compression)
An elastic material of a cellular structure having smooth, crepe, or porous surface. It is produced in various thicknesses. Sheets are limited to widths greater than 6 inches (152.4 mm). It may or may not have a nonrubber backing.
Classification: Plates, sheets and strip of vulcanized rubber, except hard rubber, of cellular rubber
NSN 5855-00-318-7185
NSN 5985-01-098-2705
NSN 5910-01-301-8472
NSN 6130-01-269-3040
NSN 5895-01-634-0630
NSN 6645-00-426-3719
NSN 2925-01-645-2948
NSN 4140-00-866-9587
NSN 5855-01-283-3730
NSN 5960-01-589-6846
NSN 6145-00-766-8437
NSN 5930-01-627-6627