If you're looking to incorporate a strap-on into your bedroom sessions, you should look for one that will be able to fit a wide range of dildos. This is key because you should be using a new dildo with every partner — and in every hole. Harnesses, on the other hand, can be more easily washed, so you can use them with as many partners as you'd like. They don't need to be replaced as often, which is why it's worth investing in one of the best strap-on harnesses.
When shopping for a harness, one important thing to know is that you want them to be snug. Ideally, they should fit slightly more snugly a than typical pair of underwear would. Since they have to hold the weight of a dildo, they need to be on the tighter side, but not so tight that it risks cutting off circulation. Another thing to keep in mind when using a strap on with a harness is that you don't want the dildo to look like it's sagging. It should protrude straight out from the O-ring, like an erect penis would.