The Rumble 25 is a single-channel solid-state bass combo rated at 25 watts into 8 ohms. It uses one 8-inch Fender Special Design speaker in a ported cabinet that weighs 21 lb (9.54 kg). The cabinet has a removable grille and a molded plastic strap handle with nickel-plated caps.

The top-mounted control panel has Volume, Bass, Mid and Treble knobs, plus on/off switches for Overdrive and Contour. The Overdrive switch adds a gritty, driven tone. The Contour switch applies a mid-scoop voicing. The knobs are vintage-style radio types and a red LED jewel shows power. The amp is covered in black textured vinyl, with a painted metal front panel and silver grille cloth.

The instrument connects through a single 1/4-inch input. A 1/8-inch stereo auxiliary input accepts a media player for playing along, and a 1/4-inch headphone output allows silent practice. There is no effects loop, line out or footswitch jack. The listed version is the 230V EU model; a 230V UK version is also listed.