- Black anodized billet aluminum backing plate - Without end cover - Takes any 5-hole Twin Cam derby cover as end cover. This ''Derby-Sucker'' will take any stock or custom Twin Cam 5-hole derby cover as outer cover; giving styling virtually endless options. The best and simplest performance air cleaner kit for your bike... period. Gain up to 21% horsepower by simply installing a Derby Sucker™ kit on your intake. The Derby Sucker aluminum one-piece backing plate features a radiused inlet to optimize airflow. The built-in breathing system features hidden channels to prevent the use of unsightly exposed breather hoses and fittings. Note: See 959805 for the replacement air filter element. Note: An optional rain sock is not available for Derby Sucker air cleaner kits.