IS300 and GS300 Xenon bulbs the same?

Checking on http://japan-parts.eu/, part numbers are as follows:

JCE10 IS300 – BULB, DISCHARGE HEADLAMP 90981-20007

JZS160 GS300 – BULB, DISCHARGE HEADLAMP 90981-20001

Visually they look identical.

Narva catalogue lists Narva 49301 is listed as fitting both applications.

http://xenonlight.com.ua/ lists a Philips D4R 42406 XenEco as fitting both applications.