These used a single platter, removable pack for 1.25Mb of data (RK02) or 2.5 Mb of data (RK03/05).

The initial controller was the RK11C which used 'flip chip' modules to build the controller on a large wire-wrapped backplane that mounted in the top of a cabinet. The latter RK11D controller consisted of 4 quad boards in a custom system unit, mounted within a CPU or expansion box. It was possible to have up to eight drives per controller.

Only the RK05 drive was manufactured by DEC, the others being rebadged Pertecs.

The RK05 drives did not use embedded servo tracks as latter ones did, but used an optical encoder to sense the position of the voice coil head positioner. A special alignment disk pack was required to calibrate the heads (which was a yearly event). It had specially recorded, off axis data bursts and a CRO was used to match the amplitudes to center the heads. They could only be adjusted out, so if you went too far, the drive had to be run down and the heads pushed back in.