When it comes to venting and porting, Bass Drum O’s gives you plenty of options. It’s easy to get creative with Bass Drum O’s because there are endless design possibilities. Bass Drum O's now come in 2, 4, 5 & 6-inch diameters! Each size is available in 8 great colors, including Black, White, Chrome & Brass. Pre-Ported Bass Drum Heads with factory-installed Bass Drum O’s in multiple configurations are also available!