I've got try out this combo a half dozen times in that really tough to dress for weather- low 30's to low 40's with precipitation. The lightweight Core base layer is super lightweight, breathes well and dries fast- exactly what you're looking for in a base layer. I prefer the hooded version as it adds a lot more versatility for a 1/2 ounce.
The Kelvin Active is also the hoody- not quite a jacket, more than a vest. It's also light, breathes well and dries fast. For insulation on the move it's perfect. Polartec Alpha Direct is the best active insulation I've found and what's used in the Kelvin Piece.
The Sitka Flash, (discontinued but still can be found on eBay, classifieds, etc) was originally put out as a wind layer. I had one when they first came out and was disappointed in it's breathability vs my other windshirts- it also runs small and mine was a size too small, so sold it. I've since found a larger size and purchased one. While it doesn't breathe great, it is very (very) water resistant- to the point of being waterproof in most situations (if all day rain is in the forecast, this isn't the hardshell I'd choose). For on/off precipitation, particularly when it's more like wet snow vs rain- it works very well. It's also much more wind resistant than typical windshirts, so if if it's precipitation + wind- the Flash absolutely crushes other windshirts. If you're sitting and glassing, this windshirt is a better bet as well. I'll still carry a "regular" windshirt and carry the Flash as a lightweight rain shell.
Obviously there are plenty of conditions where I'm not wearing all three pieces at the same time. Dry conditions the Kelvin and the Core are often perfect on their own. Same goes for high exertion in wet conditions with Flash and just the base layer- I can be comfortable in high exertion with just those two pieces down into the mid 20's. But in those cold/wet conditions, when the exertion is lower- the three pieces really compliment each other.
The Kelvin isn't a substitute for an static insulating layer, it can augment one when stationary, but designed for on the move. The Flash isn't a substitute for a dyed in the wool hardshell for prolonged and heavy rains, but for occasional showers or precipitation that reasonable snow more than rain- works very well.
Anyways, was impressed enough to jot down a few of my thoughts
The Kelvin Active is also the hoody- not quite a jacket, more than a vest. It's also light, breathes well and dries fast. For insulation on the move it's perfect. Polartec Alpha Direct is the best active insulation I've found and what's used in the Kelvin Piece.
The Sitka Flash, (discontinued but still can be found on eBay, classifieds, etc) was originally put out as a wind layer. I had one when they first came out and was disappointed in it's breathability vs my other windshirts- it also runs small and mine was a size too small, so sold it. I've since found a larger size and purchased one. While it doesn't breathe great, it is very (very) water resistant- to the point of being waterproof in most situations (if all day rain is in the forecast, this isn't the hardshell I'd choose). For on/off precipitation, particularly when it's more like wet snow vs rain- it works very well. It's also much more wind resistant than typical windshirts, so if if it's precipitation + wind- the Flash absolutely crushes other windshirts. If you're sitting and glassing, this windshirt is a better bet as well. I'll still carry a "regular" windshirt and carry the Flash as a lightweight rain shell.
Obviously there are plenty of conditions where I'm not wearing all three pieces at the same time. Dry conditions the Kelvin and the Core are often perfect on their own. Same goes for high exertion in wet conditions with Flash and just the base layer- I can be comfortable in high exertion with just those two pieces down into the mid 20's. But in those cold/wet conditions, when the exertion is lower- the three pieces really compliment each other.
The Kelvin isn't a substitute for an static insulating layer, it can augment one when stationary, but designed for on the move. The Flash isn't a substitute for a dyed in the wool hardshell for prolonged and heavy rains, but for occasional showers or precipitation that reasonable snow more than rain- works very well.
Anyways, was impressed enough to jot down a few of my thoughts
