When i bought bitfenix cable extesnions they just would fit in the power supply but just would not fit into the motherboard or the gpu. i had to use a small screwdriver to spread the metal parts inside and shred off a little but of plastic and after that it was still a bit of pain to get them to connect. You have to wiggle them around and push pretty hard. I eventually swithed to the NZXT ones and they were a much better fit. you have to look really really close as even the smallest piece of plastic can make the process really painfull.