Who ever says it has good suction is a liar.
Plain and simple, the suction cup does not stay stuck to ANY surface. You punch it once and it sways once and falls off right off of what ever surface you tried to stick it on. Horrible product because you can not punch it more than once.

Broken
The product did not stick to the table, fell of the edge and broke. I will return the product to get something different.

good with a clamp
does not stick at all fun to punch when i clamp it to my desk

Effective with Limits
I bought this speed bag for a co-worker. And it worked like it is supposed to except for the fact that it is very surface specific. It needs a very smooth surface to stick to but even than a relatively strong punch would make it slide. The best surface so far have been wooden desks. In terms of performance, it did wonders for the work day stress if you did not go ballistic.

Speed Bag
The speed bag does not stick to the desk at all. My 11 year old son tries punching it and it will not stay put. Also, he broke it the first time he hit it.