Elevate your bedroom activities with this Knuckle Up accessory that will surprise and delight you with its functionality and undeniable "cool factor." The Knuckle Up accessory is compatible with the entire range of Vac-U-Lock attachments, featuring one-size-fits-all knuckle rings that sit under a standard Vac-U-Lock plug. You won’t believe how versatile this toy is. It’s perfect for both masturbation and use with a partner.