From the manufacturer

If you want to climb with someone lighter or heavier than you, this assisted belay resistor is the answer. The lightweight device attaches to the first quickdraw and increases rope friction, allowing a lighter belayer to catch and hold a heavier lead climber's weight. Thanks to the patented cam construction, only a fall or lowering motion activates the resistance, and the rope is never blocked completely. Instead, the device facilitates smooth handling and soft catches, allowing it to be used effectively for dynamic belaying. Take on new routes with confidence with the Mammut Assist Belay Resistor.

Features

• Activates only when needed for smooth handling
• Dynamic belaying is still possible
• Allows easier, controlled lowering of heavier climbs
• Easy to release once activated
• Attaches to the first quickdraw
• Features Boost Mode: Attach the Mammut Assist Belay Resistor to the first bolt using a locking carabiner, allowing for faster engagement with larger weight differences
• Activates even when only the first quickdraw is set, reducing the risk of groundfalls
• For single ropes: 8.7-11.0mm
• Weight difference allowance: Up to 35kg. Increases to 45kg in Boost Mode

Specifications

• Weight: 220g