Product Description: The Siemens JD63T300 is a Sentron Series thermal magnetic trip unit designed for 3-pole, 600V applications. It features LI (Long-Time and Instantaneous) trip functions and is compatible with JD, HJD, HJXD, HHJD, and HHJXD molded case circuit breakers. With a bolt-on connection and 35kA@480V AIC rating, it ensures reliable protection for a 300A frame.