These look to be near copies of versions I bought from reputable sellers in Germany. They look like they may work, if you get the item that is shown in the photos.
I'll just say this. I bought my MB tools way before it was popular and spent what seemed like an ass-ton of money for a little piece of steel. Those little pieces of steel have paid for themselves in multiples since I bought them. I've read about the paperclip tool, or fork tine tool, or something that has been fashioned out of tweezers. Cool, but you aren't going to be working on 50 to 100 to 250 pens or more using that.
Get the right tool for the job. Any mechanic or HVAC tech would tell you the same thing.
I too spent lots of money on wrenches for pistons and wrenches for nib assemblies corresponding to different years and models that the pens were manufactured. Ive used them for over 10 years. They have never failed me and ive Done a lot of pens.
Ive seen these Chinese copies. Some have written that they work well and are a fraction of what I paid for mine. Not having tried one, I Cant say much about them. Just make sure you get the right wrench for your model and year of manufacturing.
By the way I looked over the Ebay posting. I think you should be specific as to what model and year pen that you need a wrench for when ordering. Not all are the same. some have different alignment of wrench pin holes. Also, A metal TWSBI wrench from a 580 or Vac 700, works just fine on the piston of a Pelican M-800 / 1000
Nicely done Meiers. Good step by step photos. Lots will learn from this.