AP12-1-51-203 is a two-pole, fully sealed hydraulic magnetic circuit protector designed for DC circuit applications with short time delay characteristics. This toggle-actuated device features a series internal configuration with hook terminals and a nominal current rating of 20 amperes. The protector provides inverse time delay trip characteristics, with no trip at 100% rated current and trip times of 0.400 to 4 seconds at 125% overload. Key specifications include a DC series resistance of 0.005 ohms, auxiliary switch rating of 3.0 amps at 120 VAC or 50 VDC, and an approximate weight of 1.8 ounces (49 grams) per pole. This circuit protector is ideal for applications requiring accurate, temperature-independent circuit protection with trip-free operation.