When it comes to venting and porting, Drum Os gives you plenty of options. Its easy to get creative with Drum Os because there are endless design possibilities.
From Big Bang Distribution: Replicating the original bass drum hole reinforcement, snap on design, with a new configuration in size and now available in eight outstanding colors. The O's allow for minimal head removal with more variety in tunable ventilation as well as external microphone access. Big Bang Distribution has made sure that the products are well packaged and flawlessly designed.