My cousin has the 4-20, with madd turrets. Theyre interchangeable. One was a large turret with a zero stop and did one revolution, the other would turn like normal turretsIf i remember correctly, there are 2 different models of the 4-20. One model has the MAD system which only allows 1 revolution of the turret. The other version has taller capped turrets and allows for additional rotation. Or did I read that wrong.