I have received three Kayfun V4 Clones. One by ToBeCo for $30.00, which is perfect in every way except maybe for some oil, some dirt, few metal shavings/chips and bad drip tip O-Rings. Which is easily fixed. It has Silver plated Beryllium Copper spring and 510 Center Pin. The other two: One from FastTech and one from GearBest for $18.00 each are complete waste of money. Even though, they are from two different sources, they both appear to be identical. Equally bad.
1. They are full of machine oil, dirt and chips.
2. Some of many holes were filled with metal chips and one was not drilled all the way through.
3. The spring, that carries Positive (+) charge is made out steel (It is attracts to the magnet)
4. 510 Center Pin is made out of Stainless Steel.
5. Here comes a really bad news: Four milled sides of the UC Upper Section Part #8 that goes into a square opening of UC Middle Section item #5 are cut 0.3mm too deep. Which made it impossible to fasten UC Counter Screw Item #9 tight enough. Because tightening the screw will not allow the lower base section to be turned by hand, therefore assemble the unit, and control the flow of the juice. If you will not tighten that screw, you could turn the lower section but will have bad Negative (-) electrical connection. I filed Seal Ring 13x1 Item #7 by 0.3mm thinner to be able to allow for turning of the base. It worked for a while, but I still got intermittently bad Negative (-) connection.
As you can see on the left side of the picture, I shorted both terminals with a piece of wire. The Ohmmeter should read something close to 0.0 Ohms, but it reads 4.23 Ohms. When I touch the bottom of the base and the middle of it with a pair of tweezers, providing the negative connection manually, it shows 0.5 Ohms. About right considering the resistance of my tweezers.
I marked problematic areas with red arrows on the picture.
ToBeCo clone is perfect. Here is my first Kayfun V4 Ni200/Rayon build (70% shaved tails). It has been working very well for several hours. Nice flavor too.