This project is very customizable. You can use various LEDs and optics combinations. This project goal is to make a "3000 lumen" light.
The required parts:
1) Housing. The housing used in this project can fit almost anything up to 35mm in diameter. (http://www.easy2led.com/index.php?main_page=product_info&cPath=65&products_id=194)
The housing has a pill which can be screwed at almost any depth inside the shell.
2) LEDs. Triple XML board and matching optics. In this project - Ledil CUTE-3 and some Chinese noname optics.
3) LED driver. The choice depends on the available LEDs and power source. In this case it is a 2.8A buck driver (http://daoriginal.da.funpic.de//data/Buck Converter/Buck Converter.pdf)
4) Switches and wires, thermal paste.
Step 1: Preparing the pill
Applied some thermal grease and installed the LED board.
Step 2: Driver installation
Step 3: Pill installation
Step 4: Rear cover assembly
Not pictured here: use zip-ties as strain relief, another possibility is to use a cable gland.