What is a Reverse Crayford Focuser?The Reverse Crayford Focuser (RCF) is a light-weight, low-profile focuser with a new revolutionary design — JMI's low-cost, high-quality answer to plastic focusers. In the reverse Crayford design, the drive-shaft pressure is applied to a bar which "pulls" the drawtube against its supporting bearings as apposed to directly "pushing" the drawtube as seen in the normal Crayford design.