I also purchased one when I got my first guinea . He didn't like it at all and just went to sleep in it. THe box said for guinea pigs , ferrets, ect. so I thought it was safe. Of course i got online and found out that it is not safe and have never used the ball again. My big gripe is that the manufactuers advertise that these are for guinea pigs and I even asked the pet store if it was safe and of course they said yes to make a sell. I know stamp stupid on my forhead .......some packaging for these balls and wheels even have pictures of guinea pigs on them. I really dont' think that most people who buy them are aware they are harmful which really ticks me off.
I am just learning from this post that the harnesses are not safe which is good that I read this because I was going to buy one but not now.