 <unk> is a synthetic version of natural rubber latex . While significantly more expensive , it has the advantages of latex ( such as being softer and more elastic than polyurethane condoms ) without the protein which is responsible for latex <unk> . Like polyurethane condoms , polyisoprene condoms are said to do a better job of transmitting body heat . Unlike polyurethane condoms , they cannot be used with an oil @-@ based <unk> . 
