Vac-U-Lock Accessories Ultra Harness and PlugIntroducing Doc Johnson's Ultra Harness. The Doc Johnson Ultra Harness with the Vac U Lock plug is one of the many accessories available that are inter changeable with the Vac U Lock System, a state of the art strap on sex system that features an adjustable waist band up to 44"and an open crotch for maximum comfort, easy access and non slip action. All Vac U Lock products are specifically designed to give you total command and control of your erotic