Buying
Sizes and shapes
Adjectives are useless here. Two numbers and one angle describe almost everything that matters about the shape of an object.
Listings describe size in words far more often than in numbers, and the words are chosen to sell rather than to inform. Slim, average and generous are relative to a catalogue rather than to a body. The two numbers that matter are insertable length and maximum diameter, both in millimetres, and any listing that omits them is withholding the most useful information it has.
Diameter matters more than length
Comfort is governed by diameter far more than by length, because tissue accommodates girth slowly and stretches lengthways easily. A difference of five millimetres in diameter is noticeable; a difference of twenty in length often is not. Anyone unsure of a comfortable diameter can measure something already owned and use that as the reference point.
What a curve is for
A curved shaft is designed to reach the front wall of the vagina, where the internal structure of the clitoris and the tissue around the urethra respond to firm pressure rather than to light touch. That is the anatomy behind the shorthand used in product names. A curve intended for prostate stimulation is usually sharper and shorter, since the target sits closer to the entrance.
Ranges built around that shape are usually listed separately, which makes them easy to compare. A category such as the inWonderstate listing states insertable length and diameter per product, which is what allows a comparison against something already familiar.
Bases, flares and retrieval
Anything used anally needs a flared base wider than the widest part of the object, with no exceptions and no judgement calls. The rectum is a muscle that draws inward, and the number of hospital admissions caused by this single omission is significant. The anal safety page covers it properly.
Texture
Ridges, ribs and bumps read strongly in a photograph and mildly in use, because tissue conforms to a surface rather than tracing it. Pronounced texture makes a real difference at slow speeds and almost none at speed. Smooth surfaces are also easier to clean, which is a small argument in their favour over a year.
Weight and balance
A heavy object held at arm's length becomes tiring within minutes, which is rarely mentioned and frequently decisive. Balance matters as much as mass: a design with the motor at the far end feels heavier than the same weight distributed evenly, and a handle that is too short turns an otherwise good object into an awkward one.
Reading a photograph
Product photography is shot to flatter, usually against a plain background with no sense of scale. A hand in the frame helps and is rare. The reliable move is to ignore the image entirely, take the two stated numbers and mark them out on a ruler, which takes ten seconds and prevents the most common surprise on opening a parcel.