Packed pixels

Anyone know where GL_UNSIGNED_SHORT_5_6_5 is defined?
It’s not in the GL_EXT_packed_pixels extension, but it is defined in glext.h, but I can’t see to find any info as to what it’s a part of.

Thanks.

I am not sure waht extension to find it in, but you can find it in the OpenGL 1.3 spec in table 3.8. (page 97)