A double strap on is used in such a way that both partners can be penetrated at the same time. One of the benefits of sexual intercourse is that it makes both partners feel good during the act.
In this type of sex toy, one partner has the short end of the harness inserted internally and the long end for penetrating the other partner.
Yes, indeed; with a double strap on, one strap can be left inside to stimulate the other part by itself.
Many double strap on harnesses come with size flexibility, which can primarily enhance the user experience.
This makes it necessary to wash it with warm soapy water, or any toy cleaner after each use, to enhance on its hygiene and durability.