Buying a sex toy can be daunting. There’s always uncertainty when you buy from a new company—it can be tough to tell whether the materials are high quality, whether they’re safe to be in contact with your most sensitive areas, and what sorts of wear and tear you can expect. But I have a shortcut to help you make the most informed sex toy purchases: the iPhone Rule.

The iPhone isn’t designed to be in direct, prolonged contact with anyone’s genitals, and I advise against trying to use one as a sex toy. But if you did, it would probably be fine, and that’s because of what it’s made out of—glass, metal, and if you have a case, silicone. Yes, many other materials go into making a phone, and not every case is silicone, but I’ve found that this is a good way to remember what to look for in a sex toy. Naturally, all of these materials have differing grades of quality, but glass, metal, and silicone are the big three you want to be looking for when shopping for a sex toy.

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Good Old Glass

This might not be the first material that jumps to mind when you think of sex toys, but it’s a tried and true option for solid-state, non-vibrating sex toys like glass dildos and glass butt plugs. When you’re shopping for a glass sex toy, make sure the packaging or website states explicitly that it’s made out of borosilicate glass. Glass sex toys are safe to use with every kind of lube, and only need to be hand-washed with soap and water to get clean.

This is the same kind of durable glass used to make scientific equipment and it’s fully nonporous. Being nonporous is important for sex toys because if there are no pores, there’s nowhere for bacteria to hide out when you wash them. If a sex t...