The Yellow Jacket 42315 Series 41 Manifold's forged body is solid brass for durability. Full porting maximizes capacity and metal valve handles are full size for easy operation. Flutterless technology means surge protector and silicone dampened movement helps minimize needle pulsation for easier, more accurate readings. Sliding double "O" ring pistons reduces wear. Easy-to-read 2-1/2" (63.5 mm) steel case gauges with 3-2-3% accuracy (Class B).|Due to the high pressures and hazardous gases used in refrigeration and air conditioning, only trained refrigeration and air conditioning technicians should use this equipment. Proper procedures must be used.