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McMaster Item# 8630K115
Neoprene Spring Rubber Sheet 3/8" Thickness, 6" X 6", 70A Durometer
In stock at $5.24 Each
Description says: Neoprene blended with elastomeric fillers produces a hard, resilient material that bends but resists breaking.
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Item# 9013K843
Ultra-Strength Neoprene Rubber 3/8" Thick, 6" X 6", 70A Durometer
In stock at $10.68 Each