ICHIBA V2 (F)15mm & (R)20mm
 

so i was told with these spacers i am required to add "back spacing" in order for my rims to fit due to the original studs being a little bit out after installment. what exactly does that mean? & where can i buy the "back spacing"?

Just bolt them to spec and throw your stock wheels back on, they do come with hub centric centers. I had 20's all around

means there's not enough depth in the voids between the lug holes on the backside of the wheel.

you can either cut the stock lugs shorter to clear the backspacing, or get the v1 type that replaces the studs.
..or run the 20mm up front. (my wheel needed slight grinding to clear the stock protruding studs, some cars do not need to grind anything).

if you're certain you wont be using aftermarket wheels in the future go ahead and cut the studs.

of course if you use high offset aftermarket wheels you can still use the wheels no issue over the spacers. :)