The Vac-U-Lock Modular Sex System is a strap-on system designed for use by Women and Men. Optional Dong, Vibrator and PPA attachments fit to the Ultra Harness 2 and provide the users with a variety of different sizes and textures to choose from. You can purchase the Ultra Harness 2 with Plug and choose an attachment or buy a complete set which includes one attachment Dong, Vibrator or PPA. Other attachments can then be purchased later and used with your Ultra Harness 2