2when to wear them
Echo material is invisible by design, which is great for hiding a door and useless when you have forgotten where you put one. These turn all of it back on: echo blocks, platforms, walls and anything painted with the coating show up normally while you have them equipped, so you can edit a hidden build instead of swinging a pickaxe at empty air. Get a pair before you start any project that leans on echo material, not after.
Buying them means talking to the Cyborg or the Mechanic while both of you are standing in a graveyard, so you need enough tombstones nearby to flip the biome. Setting that up deliberately near town takes a few minutes. They give nothing in a fight, so pull them out of the slot once the building is done. The name is a red herring, since no spectre material goes into them at all.