CDM Converter / Adapter E40 to PGZ18 - Run a Ceramic Metal Halide Lamp on Your Existing Reflector
Best for: Growers who already own an E40-fitting reflector and want to run a CDM (ceramic discharge metal-halide) lamp without buying a whole new fixture.
Our thoughts
This is a small, cheap part that solves a specific problem: your reflector takes an E40 lamp, but the CDM lamp you want to run doesn't fit that socket. Screw this in and it does. Just double-check your ballast can actually run a CDM lamp before you buy the bulb - this adapter changes the fitting, not the electronics behind it.
CDM (Ceramic Discharge Metal-Halide) lamps use a PGZ18 base rather than the E40 (mogul/goliath) screw fitting found on most standard HPS and MH reflectors. This adapter screws into your existing E40 socket and gives you a PGZ18 socket in its place, so a CDM lamp will physically fit a reflector it wasn't originally designed for.
CDM lamps are valued for their full, closer-to-natural light spectrum compared with standard HPS, which is why growers look to upgrade to them without necessarily replacing an entire fixture.
How it compares
There are a few routes to running CDM light, and this is the cheapest one.
- Buying a dedicated CMH fixture outright from brands like Sun System or Growers Choice gives you a purpose-built unit, at a considerably higher cost than an adapter
- Gavita's CMH fixtures are built for commercial-grade reliability, again at a price point well above a simple socket adapter
- This adapter lets you try CDM lighting on gear you already own, for a fraction of the cost of any dedicated fixture
The trade-off is that you're limited by your existing ballast's compatibility, rather than getting a fixture matched exactly to the lamp.
Usage guidance
This is a simple part, but it only works correctly if the rest of your lighting setup is compatible.
Fitting the adapter
Screw the adapter into your existing E40 reflector socket, then screw your PGZ18 CDM lamp into the adapter.
Checking ballast compatibility
Confirm your ballast is rated for the wattage and type of CDM lamp you're fitting before you switch it on - this adapter changes the physical fitting only, not the electrical output of your ballast.
Lamp orientation
CDM lamps are often sensitive to burning position, so check the lamp's rated orientation matches how your reflector holds it.
Technical specifications
- Adapter fitting: E40 (input) to PGZ18 (output)
- Compatible lamp type: CDM / CMH (ceramic discharge metal-halide)
- Use case: Retrofitting existing E40 reflectors
- Housing: Heat-resistant adapter body
- Brand: Omega
Who this is for
- Growers upgrading from HPS or MH to CDM light quality
- Anyone not ready to invest in a dedicated CMH fixture
- Growers with a spare E40 reflector they want to repurpose
A low-cost way to test CDM lighting before committing to a full fixture.
Our take
For the price of a couple of coffees, this gets a CDM lamp physically working on gear you already own - as long as your ballast is up to the job.
Does exactly what it should, day in, day out.
