Requires air pump with ball adapter to pump it up to make it harder
it's ok.  has an air inlet to pump it up to make it firmer, and that's not really disclosed (or at least not disclosed very well.  maybe you can find it in the reviews somewhere???) in the description, I don't think.  So to make it firmer (mine was really soft when I got it) you have to have a pump with a ball adapter.  Not everyone has those.  I had to scrounge around for one and when I finally found one, I had a few problems with getting it pumped up.  The white insert where you pump it up kept popping out.  Once I got it pumped up and put the white insert back in it worked OK, although the bumps are not as spiky as I would like, so the massage feel really isn't that spectacular.  It's mediocre.  Thus the 3 stars I guess.
Rating: 3 stars