Bought for throat play, the diameter measurements include the swirls so effective diameter is quite a bit smaller than stated, I might have to try next size larger. That said I really enjoyed getting this into my throat and then using the swirls to spin it in all the way to the base, it is quite a unique feeling! Sliding it straight out also provides a whole other set of unique sensations as the swirls sort of flop around in my throat on the way out. Have not tried for anal play yet but will soon.