When it comes to venting and porting, the Bass Drum O gives you plenty of options. It’s easy to get creative with a Bass Drum O because there are endless design possibilities. The Bass Drum O now comes in 2", 4", 5" and 6" diameters. Each size is available in multiple colors. Pre-Ported Bass Drum Heads with factory-installed Bass Drum Os in multiple configurations are also available (sold separately).