MarflexTM PG73BNNatural Rubber Soft MarflexTM black, soft, highest quality pure gum natural rubber lining. Used exclusively for HCl service. FDA compliant. For more information about this product, complete the form below or call 800-321-5583. Specs: Application: HCL Service Durometer: 30 to 40 A Pressure Cure: 30 to 40 Atmospheric Cure: 30 to 40 A PDF Downloads: Spec Sheet (PDF) SDS (PDF) Notice: JavaScript is required for this content.