Rean flexi fit control knobs black bluered cap rean f 313 s 092 this flexi fit control knob from rean has been cleverly designed with a flexible insert allowing the knob to be used on either a d flat or 6mm spline shaft this excellent feature makes the knob incredibly versatile and cost effective as it can adapt to any orientation or shaft shape meaning no new knobs are required if an application changes rean f313 s 092 flexi fit control knob black x h 13mm x 1636mm red cap