The Vac-u-Lock System is made and a patented by Doc Johnson. Vac-u-lock offers the ability to switch between different dildos and attachments. The patented plug, made of high impact ABS plastic, holds the systems attachments firmly, without any chance of slippage or accidental removal from the harness system. The variety and versatility of the attachments is legendary: from thick to thin, or long to short, it doesn't matter what you and your partner are in the mood for, Vac-u-lock delivers. In the past, Vac-u-Lock was not interchangeable with other harnesses or dildos. Doc Johnson has recently revised the line, so many new products can be used with anything o-ring compatible. Just read the descriptions carefully. If you have any questions, please contact us. We understand it can be confusing, and we want you to be happy with your choices.