Compare dimensions and bases
Measure the features that affect fit.
Find the widest insertable point
Compare widest insertable diameter and usable length separately. When two pieces have similar length but different diameters, the dimensions describe different fits.
Check the base on every size
Choose a product intended for anal use with a clearly flared base that remains outside the body. Check the widest insertable diameter and the base separately. If the listing leaves those details unclear, confirm them before buying. See Planned Parenthood’s sex toy guidance.