Split back for STP access with sewn in front panel C ring for shaft security and use. Jock Pocket is similar but packer drops in top, no split back.

Free Ball insert

Shown inside out for viewing. Shaft is dropped thru a C ring sewn into a panel attached to the inner seams of fly. Allows haft access thru fly. Ball cage for added security. Packer is against body.

Drop C ring with ball cage Free Ball insert
All in One insert