Here's a handy 3-pack of Proto-board PCBs in Adafruit Black. Both sides have a black silkscreen with some row/column markings. Note that these don't have any traces between the PCB holes, you would normally bend over a thru-hole lead to create connections. They're also good for just plain mechanical work because they are made of strong FR4. There are also four mounting holes so you can attach the PCB to your project box. These are affordable and of good quality so Adafruit decided to put them in a pack of 3. Note that the current batch of 5cm x 7cm proto-boards are green, not black - Adafruit "will try and get black again in the future but for now, this is the only colour available". Specifications 5cm x 7cm proto-board contains 18 X lines by 24 Y lines totaling 432 holes. 4cm x 6cm proto-board contains 14 X lines and 20 Y lines totaling 280 holes. 3cm x 7cm proto-board contains 10 X lines by 24 Y lines totaling 240 holes. 2cm x 8cm proto-board contains 6 X lines by 28 Y lines totaling 168 holes.
