I only ever use NGK plugs because there are standard honda fit. The part number can be found on the timing belt cover. To most people BCPR6EY-11 doesn't mean very much. The format of the part number is specific to NGK but all spark plug manufactures rate plugs the same way.

NGK Part Number Key

The Link above is an Adobe Acrobat file I got from NGK's website, it shows exactly what each digit in the part number represents.

For example BCPR6EY-11 translates into,

B = 14mm thread diameter. This is the width of the screw threads, or the hole in the head. (Needless to say this value can not be changed)

C = Hex size 5/8". This refairs to the size of socket used to screw it in. (Also can not be changed)

P = Protected Insulator Size. (Very unlikely to ever change)

R = Resistor Type. A resistor type plug will not fire until the optimum current has been reached. Mainly helps stop radio interference. (Not Required)

6 = Heat Rating. The lower the number the hotter the plug. Hotter plugs clean themselves better but can cause pre detonation. Colder plugs do not clean themselves as well. (6 is fine, unless your sitting in traffic for a couple of weeks they should run hot enough to keep clean)

E = Thread Reach 19mm. How far the screw threads go into the engine. (Also can not be changed)

Y = V-Groove centre electrode. This is the main difference between plugs, the type of electrode. Y is the standard, I prefer to use V or VX plugs. V type are a Gold Paladium electrode and the VX are Platinum. I also found that the V and VX type plugs last much longer than the standard Y's. However there also four times the price.

-11 = 1.1mm gap. This is just to say the plug is pre-gapped, I would strongly recommend that you check the gaps anyway. There are the same plugs without the -11 in the part number, they are the same just not gapped.

Basically all plugs that can be used in a 1.5x start with BCP*E or BCPR*E. * Being for the heat range, i would only use 6. 5 and 7 can be used if you need slightly hotter or slightly colder plugs. For the type of plug you can have a S, Y, V, VX. There may be others that I haven't seen yet.