Aside from obvious dangerous and/or illegal objects or substances, we also ask our players to refrain from bringing any devices that could distract their or their team mate's attention during training sessions, including (but not limited to) smartphones, cameras, tablets, laptops, or bluetooth speakers.
Improving on the court doesn't require any flash, only attention to detail and effort, and the only things that Prolific Basketball players need to up their game are comfortable shoes, athletic gear, and a water bottle.