If you have the BLV Cube kit from SeaLand, you have received PEI Steel plate as printing surface. The concept is really good, a steel plate to be kept in place with the magnets from the PCB board, it really stays in place, easy to remove and you can bend the plate to remove the print. The plate is covered with a structured surface on both sides, I personally did not like it, I like to have a smooth surface when I print. Another problem that I had was that the steel plate was changing form when the extruder was deposing metarial on the plate, the local heating of the plate was simply changing the form of the plate.
I decided it was time for something else. I found a few alternative on AliExpress and went for the Energetic PEI plate In smooth. It is a bit pricy but I wanted to give it a chance. The package arrived in normal time from China, really well packed ! Nothing could have happened to that plate (in normal transport of course !). The plate make a really good impression, the steel seems to be stronger, as it takes slightly more strength to bend it as the original. The PEI surface is only on one side, no allowing to flip it over. Put the on the Magnetic bed, it really sticks to it, this is not going anywhere.
The PEI surface is really good and the print is really sticking to it, especially at the beginning. Be careful at the beginning not to print too low otherwise, you will have some fun trying to remove the skirt or other small lines from the plate. After a few print and a few cleaning it gets better but the part is still holding firmly on the bed. A word of caution when printing, the PEI surface is not liking when it is touched by the nozzle. So printing too low or having you bed correction not active will make some nice marks on the PEI surface. However the marks do not seems to be visible on the print so not too bad.
In all, I can only recommend this plate. It sticks to the magnetic bed, it is strong and not changing form when the first layer is made, the print sticks to the plate and after a few cleaning get easier to remove it but still remains nicely on the surface. Maybe the only down point is that the plate is not both side covered, would have been nice just to flip over, but maybe I ordered the wrong one !