The Wing Sung 3008 (2017 edition) looks almost identical to the TWSBI Diamond 580AL. Already in possession of a TWSBI Diamond 580AL, a comparison will come in due course; but for now, let's concentrate on the Wing Sung offering.
Wing Sung is a Chinese pen brand who produce cheap fountain pens of a decent quality. I remember paying around £3 (including delivery) for this pen and for the price, I was impressed. Let me explain why.
Surprisingly well built, the pen is pretty solid for the price and the piston mechanism locks with a faint click. This makes posting the cap feel a bit safer. For a pen costing a few quid, it feels pretty weighty in the hand. The clip is also sturdy and ready to clip onto a lanyard/shirt pocket/anywhere you wish.
I chose the extra fine nib because of my small handwriting and though it's not the finest nib I've ever tried (The Pilot Kakuno fine holds that record so far), it is fine enough. It is smooth as butter and a pleasure to use. It's not the most ornate nib but it does the job extremely well.
If you're new to a piston-fill mechanism, this pen would be a perfect starter pen. It is at a price point where you can decide if you like the mechanism before shelling out for a more expensive one.
Overall, the Wing Sung 3008 won't be the fanciest pen you'll ever use but it does the job. How it holds up in the long term is another question and only time will tell with that one!