COKIN P Series filters?

[LifeByTheDrop]

Hi folks, I'm just wondering about using this filter system with a ND (P154) or IR (P007) filter, does the fact that there's a small gap between the camera lens and the actual filter not allow a certain amount of light in and compromise the image? Or does the system work well anyway?
Any advice on this would be much appreciated, Thanks.

[DisrupTer911]

I have the P-holder and various filters. When you mount the ring to lens and holder to ring, you use the inner most slot first and that basically blocks light from getting in around the sides.

[2005GLI]

i just got a ebay knockoff p series($5). I'm just testing out the idea of using this type of system. Can anyone recommened an inexpensive GND?