A complete head-lens-mirror kit built around 25mm mirrors and a 20mm lens. It is a natural fit for larger CO2 machines, and a deliberate rebuild project on a K40.
The ZNNRKMYO set is built around 25mm mirrors and a 20mm focus lens. That puts it a size above the K40, whose stock mirrors are 20mm and whose stock lens is 12mm. The kit is complete in its fuller sets: a head, one 20mm lens and three 25mm mirrors, enough for every position in a three-mirror beam path.
The lead option is the head alone, set up for a 20mm lens with a 63.5mm focal length. ZNNRKMYO also offers the first and second mirror mounts as separate parts, a 50.8mm head, and three lettered sets that bundle the optics.
The build is the familiar integrative style: aluminium alloy with a black oxidation coating, an air assist nozzle, a joint plate and belt fastener, and a locking ring with a plastic buffer ring over the lens. It bolts to a gantry as a unit rather than screwing onto a small head plate.
Larger mirrors are standard on bigger machines for a reason. Over a long beam path the beam spreads a little, and a 25mm mirror catches all of it with room to spare. On a K40's short path, 20mm mirrors already do that job.
| Spec | Value |
|---|---|
| Brand | ZNNRKMYO |
| Head type | Integrative CO2 laser head set |
| Lead option | Laser head, 20mm lens x 63.5mm focal length |
| Focus lens diameter | 20mm |
| Head focal lengths | 50.8mm or 63.5mm |
| Mirror size | 25mm diameter x 3mm thick |
| Set A | Head + USA lens 20 x 50.8mm + 3 Si mirrors 25mm |
| Set B | Head + China lens 20 x 50.8mm + 3 Si mirrors 25mm |
| Set C | Head + China lens 20 x 50.8mm + 3 Mo mirrors 25mm |
| Separate parts | First mirror mount, 2nd mirror mount, head |
| Body material | Aluminium alloy |
| Coating | Black oxidation, rust and corrosion resistant |
| Air assist | Air assist nozzle |
| Mounting hardware | Joint plate and belt fastener |
| Lens retention | Locking ring with plastic buffer ring |
The lead head is set for a 63.5mm focal length, 12.7mm longer than the K40 standard of 50.8mm. A longer focal length puts the focal point further from the lens and stretches the zone where the beam stays tight. The spot at focus is also a little larger.
| Focal length | Spot | Focus depth | Suits |
|---|---|---|---|
| 50.8mm | Smaller | Moderate | Mixed engraving and cutting |
| 63.5mm | Larger | Deeper | Thicker plywood and acrylic cuts |
On a machine with a motorised or adjustable bed, the longer focus is simply a setting. On a stock K40 with a fixed clamp plate, the focal point may end up below the surface you can reach. You would need to lower the work, fit an adjustable bed, or choose the 50.8mm head instead.
Whichever you pick, run a ramp test after fitting. Tilt a scrap strip under the nozzle, fire a line, find the thinnest point, and cut a focus gauge to that height.
Note one mismatch inside the kit. The lettered sets bundle a 20 x 50.8mm lens, while the lead head option is set up for 63.5mm. Decide which focal length you want first, then make sure the head and the lens you order agree.
The three lettered sets differ in two ways: where the lens comes from and what the mirrors are made of. Both choices come down to how hard and how often the machine works.
Handle all of them by the edges with gloves on. Fingerprints bake into coatings under the beam and leave permanent marks. Clean with lens fluid on a soft swab, one pass, and let it dry before firing.
Air assist protects the whole kit. The nozzle keeps smoke off the lens during cutting, and a clean lens runs cooler and lasts longer. Feed it from a steady pump and turn the flow down for engraving so smoke residue does not spray across the work.
Tighten the locking ring only until the lens stops rattling. The plastic buffer ring spreads the load, but overtightening can still crack a ZnSe lens. Keep a spare lens in its case; a crack mid-job stops the machine completely.
If you run a mixed shop, split the difference: a USA lens for daily cutting, and Mo mirrors in the positions that collect the most smoke. Mirror one near the tube stays cleanest; the head mirror gets the worst of it.
For most K40 owners, this kit is the wrong first upgrade. A drop-in air-assist head such as the Lightobject keeps your 20mm mirrors and the stock geometry, and takes an afternoon. The ZNNRKMYO set replaces the whole optical path with larger parts.
There are good reasons to go that far. Owners who have extended the bed, moved the tube, or rebuilt the gantry sometimes standardise on 25mm optics for the wider catch area. Owners of larger CO2 machines built around 25mm mirrors are the kit's natural buyers.
Similar big-optic kits exist. The XYNLHZQ integrative set also uses a 25mm mirror with D18 or D20 lenses, and ZQDWMND sells a 25mm integrative mount set in four parts. Compare lens grade and parts included rather than looks.
Look over the machine for these:
Budget an evening for the install, not an hour. Then align the whole path from mirror one using the alignment method.
Not directly. It is built for 25mm mirrors and a 20mm lens, while a stock K40 uses 20mm mirrors and a 12mm lens. Fitting it is a custom rebuild.
A 20mm diameter focus lens with a 63.5mm focal length, 12.7mm longer than the K40 standard of 50.8mm.
Each set has the head, a 20 x 50.8mm lens and three 25mm mirrors. Set A has a USA lens and Si mirrors, Set B a China lens and Si mirrors, Set C a China lens and Mo mirrors.
Yes, it has an air assist nozzle. You need a pump or compressor to feed it.