OpenGL is not the only means for extending the X Window System to support 3D. PEX [9] is an extension developed by the X Consortium to add 3D capabilities to X. The currently available version is 5.1. A future release known as PEX 6.0 is intended to address many of PEX 5.1's problems but its specification is not yet finalized. An in-depth analysis of PEX 5.1 and OpenGL 1.0 is presented by Akin [1]. Here we discuss some of the most prominent distinctions.