The Duo is made of shiny, smooth silicone, with a seam dividing down the middle. The seam isn't uncomfortable, and not felt during use, but it is there. It's fairly firm, with the toy only being flexible at the thinner parts, like where the balls are connected. The anal beads have little give, as does the vaginal ball. The handle is flexible, but will not fail.
Silicone is nonporous, odorless, tasteless, hypoallergenic, hygienic, phthalates- and latex-free. It's kind of sticky in a silicone way, and it picks up some lint.