The Glaceon Pro uses the same fill power down as the Microlight Alpine. Both are 700FP recycled hydrophobic down. Both pack small. The Glaceon Pro costs around £50 more and weighs roughly 160g less.
That is the whole question: is the weight saving worth the premium? The answer depends entirely on what you are doing with it.
This review is research-based. Specs from manufacturer data, construction analysis, and user feedback from multiple sources.
What makes the Glaceon Pro different
The Glaceon Pro is built around a different priority than the Microlight Alpine. The Microlight Alpine is optimised for value: good down, proven shell, sensible packability, reasonable price. The Glaceon Pro is optimised for weight: the lowest possible total weight for a 700FP down jacket, achieved through more technical and expensive materials.
That distinction matters because it tells you who each jacket is for. If packable down warmth is what you need and price-to-performance is the measure, the Microlight Alpine wins. If grams are the metric and you want the most refined lightweight down construction at the 700FP tier, the Glaceon Pro is the answer.
The construction details that enable the lower weight include a 20D Pertex Quantum Pro shell (against the 30D Pertex Quantum on the Microlight Alpine), a helmet-compatible adjustable hood that adds versatility for technical use, and a belay-friendly two-way zip. These are features aimed at technical hikers and mountaineers rather than everyday trail walkers.
The 20D Pertex Quantum Pro shell
The shell is where most of the weight saving happens. Pertex Quantum Pro is Rab's technical outer fabric: tighter, more wind resistant, and more water resistant than standard Pertex Quantum. Moving from 30D to 20D fabric reduces the weight of the shell meaningfully while improving some performance characteristics.
The trade-off is durability. 20D fabric is more susceptible to abrasion and snagging than 30D. It is not fragile in normal use, but it will show wear faster than a heavier shell if subjected to rough pack straps, scrambling, or regular contact with sharp objects. The Glaceon Pro is built for careful use on technical routes, not the kind of jacket you throw in the boot and forget about between hikes.
The Pertex Quantum Pro construction also provides better wind resistance and water shedding than the standard Quantum shell, which is a genuine performance benefit: the Glaceon Pro handles light rain and driving wind better than the Microlight Alpine before a shell is needed over the top.
Weight: why it matters and when it does not
At roughly 265g total, the Glaceon Pro is one of the lightest insulated jackets in the Rab range — lighter than the Microlight Alpine, lighter than the Electron Pro, and within range of the ultra-technical Mythic G.
160g less than the Microlight Alpine sounds marginal. Over a long day or a multi-day route, with everything else you are carrying, it adds up. Hikers who have thought carefully about base weight — the weight of kit they carry on every trip regardless of conditions — understand that 160g here plus 100g there plus 80g somewhere else becomes the difference between a comfortable pack and one that grinds you down on the last miles.
For day hikers on established routes with no base weight concerns, 160g is not the decision point. For anyone building a lightweight or ultralight kit, the Glaceon Pro earns its premium.
How it compares to the Microlight Alpine
Same 700FP fill power. Roughly 160g lighter total. £50 more expensive. Better shell performance. More delicate fabric.
The Microlight Alpine is better value for anyone whose primary metric is warmth per pound spent. The Glaceon Pro is better for anyone whose primary metric is grams per unit of warmth.
Neither is objectively superior. They are optimised for different things. The practical test: if you have never thought carefully about your pack weight, buy the Microlight Alpine. If you can tell me your base weight without looking it up, consider the Glaceon Pro.
Real-world warmth
Both the Glaceon Pro and the Microlight Alpine use 700FP down. The fill weight in the Glaceon Pro is lower (the lighter construction leaves less room for fill), which means the Microlight Alpine may actually be marginally warmer despite the Glaceon Pro's more technical shell.
For most UK hiking conditions this distinction is academic. At temperatures where 700FP down is sufficient, both jackets are sufficient. At temperatures where 700FP starts to feel marginal, neither jacket is the right tool — the Electron Pro with 800FP fill is where to look.
The warmth window for the Glaceon Pro is the same as the Microlight Alpine: comfortable in dry cold, useful as a mid layer in colder conditions, not designed for sustained temperatures well below 0°C.
The limitations
The 20D shell requires more care than the 30D Microlight Alpine. If you hike with a pack that has exposed buckles or compression straps that contact the jacket regularly, you will see the lightweight fabric start to pill and wear faster than you might expect. This is not a jacket to use carelessly.
At £260, it is £50 more than the Microlight Alpine for roughly equivalent warmth in a lighter package. If the weight saving is not a meaningful factor in your hiking, that premium does not make rational sense.
Where it sits in the Rab range
The Glaceon Pro sits alongside the Microlight Alpine in Rab's lightweight down tier. Below it synthetically is the Cirrus. Above it are the Electron Pro (800FP, warmer) and the rest of the high-performance down range.
The full picture of all eight Rab insulated jackets, with a spec comparison, is in the complete Rab insulated guide.
Verdict
The Glaceon Pro is a well-made, technically refined lightweight down jacket. It does what it claims: same fill power as the Microlight Alpine, meaningfully lighter, more technical construction, higher price.
Buy it if pack weight is a priority and you are prepared to look after a more delicate shell. Buy the Microlight Alpine if warmth-per-pound-spent is the measure and 160g of difference does not matter to you. Buy the Electron Pro if warmth is the priority and fill power matters more than weight.
Buy the Rab Glaceon Pro on Amazon