The ATC-XP is a variable-friction belay device with high and low friction modes.
The latest ATC-XP is now 30% lighter than the original thanks to an updated design with windows machined through the body. The Black Diamond ATC-XP Belay is a variable-friction belay device with high and low friction modes.
In high friction mode, with the live rope running through the grooves, the ATC-XP grips the rope better which is helpful if you are belaying someone bigger and heavier than you.
In low friction mode it works much like a normal belay device and runs smoothly even with thicker diameter ropes.
The ATC-XP really comes into its own when used with sub 9mm half and twin ropes, even when the ropes are icy or muddy.
When ice climbing the ACT-XP provides much more control of icy ropes when belaying and abseiling, than a normal belay device.