This is a Eaton Insulated Enclosure for Motor Protective Switch. Its part number is CI-K2-PKZ0-GR. It comes as pictured.

Specification:

• Enclosure Rating: IP66
• Height: 6.3 Inch
• Length: 5.12 Inch
• Series: XT Series
• Special Features: Frame B XTPR only or with: XTPAXFA, XTPAXSA, XTPAXUVR, XTPAXSR, XTPAXCL
• Type: Accessory
• UPC Code: 4015082196554
• Width: 3.94 Inch