The tier refers to the tier of the material, which depends on the stage of the game at which you get it. All of the values below are subject to change
Rus - Rustichromia Emb - Embers Rekindled IE - Immersive Engineering MC - Magneticraft TR - Tech Reborn PC - PneumaticCraft: Repressurized Mek - Mekanism NC - NuclearCraft AR - Advanced Rocketry