As far as I have seen I am the only provider of 99.9% Pure C1100 grade Copper Modules. I have these machined by a certified manufacturer which comes at a cost of about 3X what i can source cheap knock off "so called copper" modules from China. I refuse to chase the lowest price and sell these. There are lots of low grade Axiz standard style modules coming out of china. Beyond the lower thermal efficiency I have been seeing a major issue causing diode failures using these modules. Low grade copper becomes very brittle where it is thinnest. If you magnify an image of the lens threading on low grade copper modules you will see the threads are not absolutely flawless and have burs and chips in them. When a lens is threaded in and out more particles flake off and get in the module housing. These particles will eventually find their way to the diode window and damage or destroy the laser diode or worse for capless diodes get right on the dye causing fast degradation. So you can tell lower grade copper by looking at the threads, rounded or square edges or even the flat surfaces they should be perfectly smooth if there are pits or chips under magnification those are lower grade copper and dangerous for your diode. You can also thread a lens in and out of your module several times then tap the module on a white sheet of paper and see if any particles fall out and land on the white background.

 Also on our sold thermal back halfs we pay extra for a tough machine cut of the raised lip which makes contact with the back of the 9mm diodes and is essential for proper operation of the higher power 9mm diode. This is a hard cut as it requires a special cutting tool that can go at an angle around the threading in the back half which is the most expensive cut. If the solid back half you are using is just flat it will not make proper contact with the back of the diode since the 9mm diode presses in just past flush to ensure proper seating and side thermal contact with the diode head.

Picture shows four different modules in various configurations. One in a aluminum rail mount as a heatsink which you can purchase separately. They fit these modules perfectly and provide excellent heatsinking. Like this one.

SK-20 Bearing CNC Aluminum Rail Linear Motion Shaft Support Series Slide 20mm

The 20mm modules come with a copper diode mount, back half, spring, acrylic lens and focus ring. 

Aluminum hollow back half has room for a floating driver connected to the diode pins.

Solid Copper back which adds a great deal of mass and  presses up against the base of the diode mount  for maximum heat dissipation. 

Copper Driver Shelf back half has a machined out pocket to thermally flat mount a driver to and also has direct contact with the base of the diode mount.

Aluminum Hollow and Copper Driver Shelf back halfs work great with the Micro Flexdrive, SXD,  LSDE500, ACS1500SE, ACS5500BU or similar compact laser drivers.