These SUPER THICK cards are made from VERY expensive card stock, at least 150% thicker than store bought paper thin brands, always acid-free archival quality, and in bright white uncoated finishes so they can soak in everything you put on them. We have 3 thickness options, 14pt, 17pt, and 25pt (store bought cards are about 7pt). My 14pt cards are how thick index cards used to be in the 90s, and are more affordable. They comply with the USPS requirements for postcard thickness, only some printers can handle them, please request free samples to try in your printer. 17pt is thicker, more expensive, and does not go through printers, 17pt is perfect for thick flashcards, or watercolors. 25pt is an extremely expensive and very thick card stock. 25pt feels like a little slice of wood, it's extreme. If you want to compare thicknesses remember this, if you stack 100 of my 14pt cards they'll measure about 1.4 inches tall. 100 stacked 17pt cards will measure about 1.6"-1.7" inches tall, and 25pt cards will measure 2.5 inches tall when you stack up 100 of them. Now measure 100 of your store bought ones, they're only about 0.7" inches tall.Have you noticed that my competitors almost never mention the actual thickness of their cards? They call them "heavyweight" but they don't put the thickness measurements anywhere. I was the first to start listing heavyweight cards on Amazon (check the dates on my listings) and the first to list them under their true thickness measurement "pt". Permanent marker won't leak through. They're perfect for notes, postcards, printing, painting, artwork, and autographs. You can run them through both Laser Printers and Ink Printers and get wonderful results. They're made in the USA.