3- and 4-pin compatible fan header, with a tab so you won't plug it in backwards! Great for DIY projects involving PWM PC fans, but it should work with regular 3-pin fans, too.

I bought some generic pin headers and used flush cutters to remove some individual pins to put into this fan header.

Getting the pins through the holes can be difficult, though. I used pliers and pushed them through with some effort. I may adjust the model with a little more tolerance in the future.