same speed and pin ram but different amounts will they work together ?

[TheNewUnknownPCGamer]

I've currently got 8gb 1600mhz of ddr3 ram 240 pin and want more and im looking at an 4 gb stick with exact same specs besides memory will they work together ?

 

[DRagor]

Maybe. There's no way to tell what will be effects of mixing RAM stick not bought as a kit. Sometimes it works straight up, sometimes it will require changing some settings in BIOS manually, sometimes it will not work no matter what you do. Using sticks with same stats maximizes your chances of success (size does not count here), but not to 100%. Buy a kit, or prepare plan B if you go for adding single stick.

 

[lordmogul]

Theoretically it should work. That's why there is a standard for it.
If it runs well is on a different page. you most likely lose dual channel, and depending on the circumstances could not be able to run at the same clock as more modules means more stress for the memory controller.
But the chances that it will work are good.