This is the Apeks AT20 Scuba Diving Regulator 

Features:

• AT20 Predecessor to XTX20
• Represents an Excellent Value
• Ideal Entry-Level Regulatorv
• Can Spoil Divers In-a-Hurry
• High-Performance Regulator
• Designed for Water Temps Above 50°F (10°C)
• Nitrox Ready Up to 40% O2 Out-of-the-Box
• First Stage: APEXS AT20
• Balanced Diaphragm Design
• Consistent Performance from Start of Dive Until End of Dive
• LP Ports: 4 Port 3/8 UNF Thread
• HP Ports: 1 Port 7/16" UNF Thread
• Body: Marine Brass, w/Chrome Finish
• Second Stage: APEXS AT20
• Pneumatically-Balanced Second Stage
• Smooth, Easy Breathing
• Large Purge Button, Easy to Operate w/Thick Gloves
• Integrated Venturi Control:
• Provides Performance Boost at Depth
• Prevents Unwanted Free-Flow at Surface
• Extremely Efficient Exhaust Valve Improves Breathing Performance
• Compact, Integrated Exhaust Tee