The card is 300gsm (thick!) with a matte finish, so you can use alcohol markers like Sharpies without any bleed through at all. On the reverse is the standard postcard format with room for a message, stamp and the address you're sending it to. The pack of 10 is just £4.99, making each postcard under 50p- fantastic value! UK postage is just £1.50 and USA shipping is a little over $4.
Here's a postcard I just coloured with Faber Castell Pitt Pens and some glitter because why not :)