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Carabiner Design, Evolution, & The FS Mini

Metolius FS Mini ii

Note: this text was originally published by Adam S. on an earlier version of Climbing House.

I was browsing the local gear shop yesterday when I stumbled upon the Metolius FS Mini carabiner for the first time. It is shockingly small, so small in fact, that I think it has lost much of the functionality of a traditional carabiner.

This realization led to a review of the existing lightweight’ biners, and the design discussion that follows.

Lightweight Carabiner Review

Left to Right: BD oval (for reference), Mammut Moses, BD Oz, CAMP Nano, Metolius FS Mini

I compared existing wire gate carabiners based on price and weight (quantitatively) and size (qualitatively). I did not include any ‘biners with special features (such as a “clean” nose) to hold constant as many variables as possible.

The graph above shows the general relationship between ‘biner cost and weight. Lighter’ biners are typically more expensive. The most interesting points on this figure are the ‘biners that deviate further from the best-fit line.

It is shown that:
1. The Metolius FS Mini, Omega Dash & CAMP Orbit are more affordable than expected.
2. The DMM Phantom is particularly expensive. This is probably due to the cost of import and their general design & production.

Regarding size: I feel like the FS mini is too small for me to use comfortably. The BD Oz is even a little small, as my finger still gets stuck in it when clipping. That said, I own a bunch of BD Oz carabiners, and overall I’ve been pleased.

Design Discussion

So objects evolve through time. In carabiners, there are two distinct evolutionary paths: improved performance and reduced weight. BTW these paths are not mutually exclusive.

Improved Performance

Refer to the image above for some of the many performance improvements introduced to carabiner design.

Reduced Weight

There are a bunch of design concepts that can be implemented to reduce weight. Designers have mainly used shape factors (overall shape and cross-section), material, and size.

So there are some problems:
1. To reduce the weight of the object, the size is reduced. As the size is reduced, usability is also reduced.
2. As weight is reduced, strength is also reduced.

The wonderful thing is these problems have been solved before, many times, in other industries. In The Innovation Algorithm, the author lays out principles that have historically worked to solve basic contradictions. Based on his easy-to-use tables, I propose several possible solutions to the FS Mini problem.


1. Change Materials. Peter Metcalf of Black Diamond said that he expects plastic carabiners in the future.

2. Reduce usable lifetime. It is probably related to #1. Provide less durable carabiners for very specific (not every day) uses.

3. Change the gate design. The main functional problem with the smaller carabiner is that my finger gets stuck in it. Omega Pacific uses a gate swing that is offset from the spine of the carabiner. This increases the biner opening width. This design, similar to the gate opening 90 degrees from the spine or out instead of in, would solve the functional problem.

4. Design a gate that stays in two positions- open or closed. This would stop the gate from “grabbing” the user’s finger while clipping.
This close-up of the Black Diamond Oz carabiner illustrates using the shape factor to reduce weight.

Climbing equipment has evolved, and it will continue to evolve. I hope to see some of these suggestions implemented in future models of lightweight carabiners.

Some related articles that might interest you:
1. SuperTopo review of the FS Mini
2. Backcountry.com article on carabiner production
3. Rockclimbing.com general discussion on the FS Mini

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