Cree XHP70 up to 4022 Lumens and XHP50 up to 2546 lumens - Multi-die leds.

[finges]

@Fritz t. Cat

What would be a good regulated linear driver for the XHP50 and two 18650s? Are there other choices than a Qlite with Zener mod.? I expect to have a 20 mm. wide space in the pill.

You can use the LD-2 driver LD-2 : 6Amps pwm-less linear driver - info and FAQ thread