Brady M21-375-423 21' Length, 0.375" Width, B-423 Permanent Polyester, Black On White Color, BMP 21 Mobile Printer ID PAL And LABPAL Printer Label B-423 Permanent polyester is UL recognized for outdoor use on glass, thermoset polyester plastic and polyvinyl fluoride plastic surfaces to support solar panel identification applications Recommended ribbons are brady series R6000, R6000HF (low halogen), R4400 (colors - red, blue, green, white), R4900 and R6200 (alternates) Agency approval(s)/compliance are AGA approved, CSA approved, halogen-free (DIN VDE 0472/parts 815), UL recognized Autoclave, freezer environment with smooth, textured/rough surface Printer compatibility is BMP21, ID PAL, LABPAL