Rock Island-liveried HO GP7R Locomotive with DCC and Sound, ROCK #4506, is a detailed HO-scale rebuild of the GP7 switcher designed to bring authentic mid-century diesel power to modern layouts. It features a DCC decoder with SoundTraxx Tsunami2 and two cube speakers for realistic engine, horn, and bell sounds that operate on both DC and DCC. The model uses a Genesis driveline with a five-pole skew-wound motor, precision flywheels, and a multi-link drivetrain for smooth, quiet operation, backed by a heavy die-cast frame for traction. DCC-ready Quick Plug plug-and-play technology with a 21-pin NEM connector makes decoder upgrades straightforward, and body-mounted McHenry scale knuckle couplers (Kadee-compatible) ensure in-scale coupling on standard HO track.

Rock Island styling is reflected in road-name details such as non-dynamic with roof access hatches, early Pyle headlights, a firecracker antenna, and early pipe-style handrails, topped by a Nathan P5 horn. For unit 4506, late small louver battery box doors and a standard EMD fuel tank are included, with an optional whip antenna in the packaging. The model features see-through cab interiors, etched radiator and fan grilles, fine-scale Celcon handrails, RP25 wheel contours for compatibility with popular HO track, and bidirectional LED lighting for consistent headlight brightness. It is NMRA-compatible with a CV chart included, and minimum operating radius is 18 inches (22 inches recommended) for best performance.