Selected features of the BR-21 include an index notch on the head to help divers find the hole which improves rod insertion even in a low-visibility environment. The beveled seat keeps the electrode at the ideal angle and the groove eliminates electrode wiggle. The over-sized head is easier to hold and the handle and head are from hexagonal stock for sure gripping by a gloved hand. The BR-21 also includes a resistance O-ring on the shoulder to ensure tension when the head is tightened and increase head life.