The TremorPak was Performance/InterAct's version of Nintendo's Rumble Pak. Across it's numerous iterations, it included a vibration speed switch, featuring high and low (power-saving) modes.
Many budget third-party manufacturers during this era sold products where the image on the box did not match the product inside the box. At least one example of this variant containing the original wedge-shaped TremorPak insider the "Nintendo Style" box has been found.
Trivia
Performance changed the packaging for their TremorPak in 1998 to a green box. Like most of the 3rd party companies during this era, there was no differentiation on the product itself, so the box remains the only unique part of this release.