Yes, you can use STP 3in1 and 4in1 models for sexual intercourse, at your own risk. Sexual penetration is able if only a condom is used. This medical silicone, the prosthetics are made of, are totally safe but it was not intended for sexual penetration. If you choose to have sex with FTM STP packer - the use of condom is required. It is recommended to use water-based lubricant only. Silicone lubricant will damage your product. Using a condom is the best way to stay safe and healthy for you and your partner. It helps to keep your prosthetic in a good condition, too. Our models are ultra-realistic, so you and your partner will have an amazing and unforgettable experience! Please note: rough or very intensive play may damage your prosthetic.