Your internal flash will work without removing the HC-4A Hot Shoe Cover. The only time you'll take it off is to use an external flash, and high-tolerance machining ensures it won't slip out on its own.
In place, it protects the camera's flash contacts from rain and dirt, eliminates snagging when you pull the camera from your pocket, and it simply looks good.
Most market existing hot shoe covers don't support the pop-up flash function. In other words, while user inserts the hot shoe cover into the hot shoe socket, the build-in sensor will be turned off which causes the pop-up flash to be in no induction state. The HC-4A help users solve this problem.
HC-4A Compatible cameras:
Canon EOS 700D, 650D, 600D, 550D, 500D, 450D, 400D, 30D
Canon EOS Digital Rebel T1i, XSi, XTi
Canon EOS Kiss Digital X3, X2, X
Canon POWERSHOT G10,G11, SX1 IS
Canon POWERSHOT SX10 IS, SX20 IS
Canon EOS 1000D, 1100D Digital Rebel XS
CANON EOS 7D, 550D, 50D, 40D
CANON EOS 1D MARK IV, III
CANON EOS 60D, 50D, 40D
CANON EOS 5D MARK II
CANON EOS Digital Rebel T2i, KISS X4