R-Box field-mount enclosure for DIN rail-mount instruments and I-Box surface-mount instrument enclosure accommodate a range of instruments. The R-Box is designed to meet standards for enclosing indoor and outdoor electronic instruments approved for use in hazardous locations. It meets Type 4X and IP66 environmental ratings and is resistant to ultraviolet rays and chemicals. Its high-impact structure protects instruments even in harsh field conditions. The I-Box mounts securely on a surface using standard key-slotted mounting holes. It has standard internal widths of 9, 12 and 15 in with depths of 3 and 6 in. The lightweight and chemical-resistant structure is suitable for indoor installations.