The main thing you notice about this top is that it's extremely light and packs extremely small - less than half the weight and pack size of my normal walking windproof.
The fit is very slim - I have 36" chest but bought the 38" (Small) and it's still pretty snug but does give freedom of movement. The waist has an adjustable elastic cord but it's already a fraction small as it sits at the top of my hips, so rides up into my actual waist where it's about right.
The sleeves are half-elasticated at the cuff and seem to work well for me, but aren't adjustable.
There's a good sized chest pocket for a key, parkrun barcode or whatever, but no side pockets to keep hands warm while standing around before/after.
Just tried it for the first time on a gentle 30 minute run, 3 degrees C in December and it gives about the right level of wind protection without getting too warm; just needed to partly unzip halfway round for more ventilation. For anything warmer, longer or faster you'll need to stow it in a waistpack.
The fabric is 100% nylon, very fine and soft but with a faint rustle - but I didn't really notice this once outdoors. It's somewhat breathable but not really wicking, so it was visibly damp on the inside surface after my run so will always need careful airing.
