Poly is a short name of Epoxy gloss protection of the brass plate. After a while it might happen that the color on a luopan without this protection will disappear and the characters are hard to read (see left image). The Poly protection is available for all PREMIUM and CLASSY luopan.
That will not happen with the Poly protection (see right image). This investment for a new luo pan is worth for Masters and users who uses the luopan frequently.
In combination with the red gloss painted frame, your luopan becomes a first class tool.
Left part new luopan without Poly protection Right part new luopan with poly protection
Read the details here