The Glass Viewer is a block added by the XyCraft mod. Similar to Optifine's connected glass feature, adjacent Glass viewers will connect their textures to appear as one large glass piece. Glass viewers can be broken by hand and recovered, but are broken faster by pickaxes.
Glass Viewers are useful when using XyCraft's Multitank to see the level of liquid inside the tank visually.
Recipe[]
XyCraft Multitank[]
Glass Viewers count as valid walls to Multitanks, except when used as corners or edges. They can be used to check the contents of a multitank at a glance without accessing the GUI.