Viton elastomers "non carbide sealing material". I'm not 100% sure what pump type this fits so just to be clear you should measure your extension shaft diameter but I'm almost positive that this if for a NM031 standard configuration progressive cavity pump. This seal is an non encapsulated compression spring type seal for pumping various materials that users don't care about getting stuck or clogged in the rotating spring assembly. Mostly used for non food grade applications.