Affordable and funktioniell, but no documentation

I use the converter for a Arduino per Mini 3.3V.
Conversion to 3.3V is not quite self-explanatory. On the underside of the board is an option to select the output voltage, either 3.3 or 5 V is (must be set by Lötdurchzug to this voltage).
The Board has from the outset 5V output voltage, the VCC pin and the 5V option are poorly visible through contacted. But when you scrape it with a scalpel or a fine screwdriver and soldering to 3.3V, then that works too.

Edit:
Differentiation between modules by udev rules is not easily possible, since all have the same idVendor, idProduct and serial:

dev / tty / USB0
ATTRS {idVendor} == "10C4"
ATTRS {idProduct} == "EA60"
ATTRS {serial} == "0001"

dev / tty / USB1
ATTRS {idVendor} == "10C4"
ATTRS {idProduct} == "EA60"
ATTRS {serial} == "0001"

If that does not bother - they work with me after about six months of continuous operation as before with no problems.