Materials
Silicone
Silicone is the default material for soft intimate products, and for good reason. The detail that separates a good one from a poor one is invisible on the shelf.
Silicone is a polymer built on a backbone of silicon and oxygen rather than carbon. That backbone is the source of every property that matters here. It is chemically stable, it tolerates heat that would deform most plastics, it does not support bacterial growth on its surface, and it can be formulated anywhere between the firmness of a car tyre and the softness of a jelly sweet without changing the chemistry underneath.
Platinum cure and tin cure
Liquid silicone has to be set, and there are two common ways to do it. Platinum cure uses a platinum catalyst and produces a fully reacted material with no by-products left behind. Tin cure, formally condensation cure, uses a tin compound and releases small amounts of alcohol as it sets. Tin cured silicone continues to shrink slowly, carries a faint residual odour and degrades over years rather than decades.
For an object that goes near mucous membrane, platinum cure is the one worth paying attention to. It is what medical and food applications use, it survives boiling without change, and it does not develop the sticky surface film that older tin cured pieces eventually show.
The lubricant rule
Silicone lubricant and silicone objects are chemically related, and that relationship is not a friendly one. Given time in contact, a silicone lubricant can soften the surface of a silicone object, leaving a tacky patch that never quite recovers. The rule is therefore simple: water based lubricant with silicone objects, every time. The compatibility page sets out the full grid, including the cases where a hybrid formula behaves differently from a pure one.
Not every silicone reacts, and a small patch test on the base of an object will show within a few minutes whether a given combination is going to be a problem. The reason the blanket rule persists is that the test has to be repeated for every new combination, and a water based lubricant removes the need to think about it at all.
Firmness is a design decision
Shore hardness describes how much a material resists indentation. Soft silicone in the range around Shore 10A feels yielding and absorbs vibration. Firm silicone above Shore 40A transmits vibration efficiently and holds a defined shape under pressure. Neither is better in the abstract. A firm shell with a soft outer layer is a common compromise, and it explains why two objects with an identical motor can feel entirely different.
Firmness also changes cleaning. A very soft surface picks up lint and dust from the moment it leaves the box, which is a nuisance rather than a hazard, and is the reason storage in a bag matters more for soft pieces than for rigid ones.
Cleaning and heat
Silicone tolerates hot water, mild soap and, for objects with no motor inside, several minutes at a rolling boil. Anything containing electronics stays out of the pot and is washed by hand instead. Abrasives are the one thing to avoid, since scratches in an otherwise non porous surface create exactly the channels the material is chosen to avoid.
Shops that sell across this category usually separate silicone pieces from blends in their own listings, which makes the material easy to filter on. A retailer such as inWonderstate states the material on each product page, and that is the field worth reading before anything else on the listing.