Professional quality black core cardstock that is used by modern commercial TCGs in industrial offset printers.
Letter (8.5*11in) sheets. Fits in standard consumer printers. A rear-fed laser printer is the most compatible printing technology. It will likely jam any non-rear-fed printer. NOT COMPATIBLE WITH NON-UV INKJET PRINTERS.
Back fed laser printers (check the paper thickness gsm specification of your printer, though it is usually understated) produce good results. The melted toner acts as a sort of varnish (water resistant, contributes some snap) which is on commercially produced cards. For higher quality, you will need to tweak the settings of your printer and color management.
330gsm is closest to MTG cards. (34mil thickness)
(closer than 300gsm, 310gsm, or 320gsm)
310gsm is closest to Pokemon cards (.3mil thickness)
(closer than 300gsm, 320gsm, or 330gsm)
Smooth Silk Finish (matte with a slight shine). Surface is coated. Pigment based inks generally will not absorb. NOT embossed or linen finish.
Coated surface: Consumer pigment inkjet ink will generally not absorb. Laser or UV (flatbed DTF, UV inkjet) are the only endorsed printed technologies. Use other printing technologies at your own risk. You may need to adjust your printer settings.
Each letter size (8.5*11in) sheet fits 9 poker (63*88mm) MTG/PKM sized cards.
For professional industry quality, a flatbed DTF printer is best because it uses UV ink and applies a varnish layer. There are combo flatbed/roll DTF printers that can also be used for hot stamping/foiling. Great quality results can still be obtained from laser printers.