Polyetherimide (PEI), also known by Ultem®, is a high-performance thermoplastic with excellent mechanical, thermal, and electrical properties. Laser cutting and laser engraving of PEI are possible with a 9.3 micron or 10.6 micron CO₂ laser. Charring will occur with both laser wavelengths, although it will be less severe with the 9.3 micron wavelength. Due to charring, laser cutting and laser engraving of PEI are not recommended. Laser marking of PEI with a CO₂ laser produces an indelible surface mark that can be lighter or darker, depending upon the additives used in the formulation. PEI does not readily absorb the energy from the 1.06 micron fiber laser and is not recommended for this material.