On a 12.5 mm rope, which Prusik size is recommended?

On a 12.5 mm rope, which Prusik size is recommended?

• A. 7mm
• B. 8mm
• C. 9mm
• D. 10mm

Answer: (C)

The key idea is choosing a Prusik that will bite reliably on a rope of that diameter while still allowing you to slide and release it when needed. For a 12.5 mm rope, a Prusik around 9 mm hits a sweet spot: it’s large enough to create good friction against the thick rope, giving a solid hold under load, yet small enough to wrap and release without binding too aggressively. If the Prusik is too small (7–8 mm), it won’t bite as well on a thick rope, reducing grip and increasing the risk of slipping under load. If it’s too large (around 10 mm), the hitch can bind more than desired, making it harder to slide and adjust when you’re moving or cleaning the knot. So, 9 mm provides the best balance for a 12.5 mm rope.

The key idea is choosing a Prusik that will bite reliably on a rope of that diameter while still allowing you to slide and release it when needed. For a 12.5 mm rope, a Prusik around 9 mm hits a sweet spot: it’s large enough to create good friction against the thick rope, giving a solid hold under load, yet small enough to wrap and release without binding too aggressively.

If the Prusik is too small (7–8 mm), it won’t bite as well on a thick rope, reducing grip and increasing the risk of slipping under load. If it’s too large (around 10 mm), the hitch can bind more than desired, making it harder to slide and adjust when you’re moving or cleaning the knot. So, 9 mm provides the best balance for a 12.5 mm rope.