The width of the strap itself. It is the main figure hardware is chosen by: a buckle, keeper or snap hook has to take this width; otherwise the strap puckers or will not pass through.
The thickness of the strap or webbing itself. It decides whether the material passes through the slot of the hardware and how well the item holds its shape: thicker material is stiffer and bends less easily; thinner material folds better but wears through sooner. Choose hardware by width; watch the thickness at the slot and when riveting.
The colour of the version. On hardware it is the colour of the finish, on everything else (webbing, rope, leather dyes, edge paint, textiles) the colour of the material itself. A shade in a photo and on a screen differs from the real thing, so when ordering more for a production run already under way, compare by the name of the shade, not by the picture.
A variant of the same item that differs in construction, shape or surface: for hardware, for example with or without a lock, straight or curved, or all-metal; for straps and webbing, smooth, braided, hair-on or with a reflective stripe. Variants usually share the dimensions and differ in handling or looks.