As usual, baseball caps will have 6 panels, 6 eyelets, pre-curved peak, structure ,with velcro closure.
The material will be 100% cotton twill ,brushed or not. Or 100% polyester caps ,or polyester and cotton mixture caps.
Cotton twill baseball cap is popular,but if you want to cheap caps, 100% polyester cap is the best choice. www.ytcheadwear.com/pic/big/185_0.jpg
You can see this cap, we often export at least 100,000pcs of this model cap.
And client can make his logo by printing on the front of panel.
This is the general description of baseball cap hats.