What is this?

Im sorry i dont have a picture, but i noticed professional pitchers warming up their arms with something that almost looks like a blackjack/slapper or something like that. They use it by throwing as hard as they can without letting it go. If i find a photo ill post it but just pay attention to the majors and that pitcher who was on Real Sports with Bryant Gumbel. He was using it to strengthen his arm, rehab and gain velocity. Any info would be greatly appreciated. Thank you.

I have no clue, if you can get a picture of it or a video of it I’d like to see it.

If your talking about the one with the Seattle Mariner guy with screws and plates in his elbow then in the clip I saw it was a weighted/medicine ball and a towel were the two objects he did the throwing motion without releasing them.