GG&G, Inc. Side Saddle Shell Holder, Fits Mossberg 500, 590 12 Gauge, Angle Facilitates Bottom Loading of the Magazine Tube and Top Loading of the Chamber, Black Finish GGG-1515 The GG&G Mossberg 590 Side Saddle and 500 Side Saddle Shell Holder facilitates loading the mag tube and the chamber. Compatible with the short tactical length forearms only. Longer length sporting forearms will need to be replaced prior to installation of the Mossberg Side Saddle.