Videos comparing the iPhone built in microphone with this microphone and the SP-AT831-IPHONE:
The microphone is very small - about the size of pencil eraser tip (roughly 1/4" in diameter 1/2" long ). The cable is terminated in small 3.5mm (1/8 inch) 4-pole male connector.
Using this microphone instead of the built in microphone on the phone will result in greatly improved audio quality. Listen to the video above for comparison!