3.1V at 400mA on a sunny day. It will charge cycle lights, and a Google Pixel 6 slowly charges, however 2 different phone powerbanks rejected the supply as being too low voltage to charge.
3.1v and 400mA is approx 1.25Watts so less than 50% of claimed 3W output, but you probably suspected this, hence you're reading the reviews.
Panels appear to prefer laying on a horizontal surface for general light rather than directly facing sun, when the current peculiarly drops, so they are efficient and no doubt helped by the dimple coating which helps collect the photons. 147mm long by 114wide, roughly the size of a male hand.
On the back the USB wire has been heat glued in, so it's reasonably well connected by would require some extra strain relief (tape, or more glue gun glue).
Arrived in UK in approx 12 days. Paid four GBP, and bought two, so the values above are measured across both panels. The results were near identical for each so they are consistent.