The X-Ray Mod is a functional mod that lets the player see through blocks among other features such as showing coordinates and the use of a light setting when in dark places.
THIS IS NOT A MOD FOR USE ON MULTIPLAYER SERVERS! Most, if not all, servers block X-ray mods because using them counts as cheating in the server and might result in a ban. It is strongly advised NOT to use this mod in multiplayer.
X=See only ores and lava
R=only see Redstone related things
L= give your self light when in caves or dark areas