There are two reasons VT05 diaphragms are not currently labeled.

Under our old labeling system which consisted of "plugs" with labels as part of the mold no 0.5" diaphragms were labeled because the mold was physically too small for this type of system.

More recently we are converting to a laser labeling system which allows us to label 0.5" diaphragms.  However, this cannot be used with any Viton diaphragms because this process produces fluorine gas.