The basic shape of a butt plug is always the same. The tip is fairly small and rounded for easy insertion. Then the body expands until it reaches the maximum diameter. Toward the bottom the toy narrows again to give the anus something to ‘grip’. The very base expands again to keep the toy from sliding completely into the rectum.
Despite all butt plugs following the same basic form they can look quite different. Beside ‘regular’ plugs (pictured on the right), butt plugs can be shaped like a penis or other objects. Also, some butt plugs have feathers or hair attached to them, giving the wearer a animal like tail.

Butt plugs come in all sizes from the size of a single finger to several feet in length. The largest toys are sold only for display and are not meant for insertion. Most people select anal toys to match the size of a penis however, for anal training larger toys are used.
For beginners small toys are recommended, especially if used in preparation of anal sex. As a reasonable minimum, 1” (2.5 cm) thickness is recommended. Otherwise the toy has little to no stretching effect on the anus and because of the slender body, the sphincters has no way of gripping onto the toy to keep it from sliding out.

There has been much debate about the duration for which butt plugs can be worn. Pro anal training people argue that since the rectal cavity is usually empty, a small to medium size butt plug does not interfere with internal organs. However, more cautious groups warn that the friction butt plugs create on the anus, the walls of the rectum and, for me, the prostate gland needs to be taken into considerations. This said, scanning the web many stories can be found of people wearing butt plugs virtually constantly without ill effects (see anal training).

Lubrication is very important since the anus and rectum are not self lubricating. Especially beginners to anal sex should use generous amounts of lubrication. Make sure that the material of your of your butt plug and the lube used are compatible (more here).

Butt plugs need to be cleaned very carefully before and after use. Use warm water and a mild soap. Some plugs (usually made of Pyrex or silicone), are dishwasher safe. A condom is often a good idea to protect your toy.