Montane Krypton, large, arrived today, 2 days from order. I got the right size. Its just perfectly fits me all over. Which is odd, this is 5th Montane top I have.
The Montane Litespeed, in medium is baggy all over, in fact I layer it over a Patagonia Sweater to boost its insulation or protect the fabric when required, it even fits over a high-loft down like Montbell Alpine Light, but removing some loft.
The Montane Prism, in medium, is a little baggy, and has more room than this Montane Krypton but Prism medium has slightly shorter sleeves than Krypton large.
Montane Velo, is in medium is a little tighter than this Krypton large across the chest but the same arm length.
Montane Slipstream Gilet, in medium is a little tighter but not by much, than this Krypton large.
So if it weren't for the "L" on the Krypton garment I'd says its a medium. Perfect fit though, sleeves, torso, hood, everything. I just need to figure out what it is for.... more active use when a Litespeed not enough, chilly-weather rushing around town on a bike going indoors/outdoors and need a good wicking? A tight-fitting non-stretchy garment is a puzzle as to its intended purpose.
On Kitchen Scales (not accurate on absolute but use as a sign of relative), Litespeed 150g, Prism 350g, Krypton 400g - so yes a 40g Primaloft insulating jacket is a little lighter than the lightly insulated Krypton, if you were packing for insulation then the Krypton won't win.
FYI for any cyclists out there, it has nil reflective piping at all, apart from the Montane logo on one side of the hood, but that probably makes it look a little smarter. That might be one thing to use this work, not backpacking at all but over a work shirt when you need a bit of insulation?