The ZN-HK4 has been designed for the CW straight key operator that prefers the knob being close the the table top. This has been accomplished by modifing the lever arm of the ZN-HKIII and eliminating its knob and skirt combination. The ZN-HKIII can not be modified to this arrangement.
The ZN-HK4 features 6 ball bearings, silver contact points, spring for return, and stainless steel screws. The adjustment screws for contact spacing, spring tension and lever arm angle are 8-32 stainless steel thumb screws with knurled nuts for locking. It is built on a 2 1/2" x 6 1/8" x 5/8" steel CNCed base and weighs 3 pounds.
The ZN-HK4 is wired with a 1/8" stereo plug wired to tip. You may have to change the plug if your rig has different requirements.