Comfort
The Onyx features a flat construction of the waistbelt and leg loops with EVA foam and breathable fabric. While the Onyx was considered one of the least comfortable harnesses tested, it also wasn’t unbearably uncomfortable as it still did an admirable job when hanging. Testers appreciated the breathable fabric and the comfortable feel while wearing the Onyx. The leg loops of the Onyx lack adjustable buckles and instead include stretchable elastic to create a snug fit against the legs. The construction of the leg loops in this manner create a simple and streamlined feel but can make it harder to find that snug, tight fit that can increase the comfort of a harness when hanging for prolonged periods of time.

Adjustability/Smooth Buckles
The Onyx has one adjustable buckle on the waistbelt. Made out of stainless steel, Singing Rock calls it the Rock & Lock and it was popular with testers for the way webbing pulls smoothly through it, cinching down with ease. Sometimes the buckle was harder to release, in particular when the harness was cinched down really tight. Part of the difficulty in releasing it could be that it’s a lot slimmer than other buckles tested. But, the flip side of that is that testers didn’t notice slippage of the buckle during use. One nice feature of the Onyx’s buckle is the ease of completely undoing the buckle and then redoing it. This is thanks to having the second buckle open, in the shape of a hook. Thus, you thread the waistbelt through the first buckle, which is wide and easy to do and then you can easily slip it through the hook of the second buckle instead of having to thread the nylon through the buckle. 

Gear Loops
The gear loops on the Onyx were some of the most popular gear loops tested. Four contoured, rigid gear loops grace the sides of the Onyx and were popular with testers for their ease in accessing gear. Their contoured shape is flattened where the gear resides, creating a nice working platform for gear to hang and be most easily accessed. The gear loops were spacious enough to carry plenty of draws for a sport route or cams for a trad route. The only downside was the lack of a haul loop for tagging a rope behind. 

Features
The Onyx’s greatest feature may be its price. At $49.95 the Onyx represents a great value for a harness that performs as well as it does. Otherwise, the Onyx lacks some of the flashy features of other harnesses and keeps things relatively simple. Testers appreciated the bright red belay loop that stood out clearly from the yellow and blue elsewhere on the harness. This feature was particularly nice with newer climbers who sometimes struggle in understanding what part is the belay loop. An interesting feature on the Onyx is what Singing Rock calls the BMI, Body Mass Index, a method of threading the nylon waist belt strap through the padded portion of the waist belt to help show a proper fit and to keep padding between the body and the nylon strap. 

Versatility
The Onyx is reserved for rock climbing use, both sport and trad, and primarily in the single pitch realm. While tolerable for hanging, climbers looking for a multi-pitch harness will likely miss the inclusion of a haul loop or rear gear loop for extra kit. Ice climbers will find it more difficult to use because of its lack of ice clipper attachment points and lack of adjustable leg loops. Hence, the Onyx is great at what it is, a single pitch rock climbing harness, lacking the broader versatility of other harnesses tested. 

Weight
At 340 grams (12 ounces), the Onyx is admirably light compared to other harnesses tested although it’s still a couple ounces away from the lightest harnesses tested.