Joe pretty much has it.
The standard 5/8" round padded weapon is your best bet, with some type of pvc, fiberglass rod or carbon fiber tube core.
Other construction methods will be evaluated on a rep by rep basis, but still must conform to the basic weapon guidelines.
Latex weapons can also be brought for inspection, but must have a non-latex replacement rep checked in at the same time.
Absolutely no metal or wooden core weapons will be accepted.