The most obvious change in the redesign was the removal of the front-loading Zero-Insertion-Force (ZIF) mechanism of the cartridge slot in the original NES-001 model. In that system, the user had to first open the lid of the case, slide in the cartridge, then press it down. The large space inside allowed plenty of room for dust to settle and the contact heads were almost impossible to access and clean without disassembling the system or using the official cleaning kit. Wear and tear was another problem; with continued use, the precision of the mechanism deteriorated and the user would have to poke and nudge at the cartridge to move it to a position that would be read correctly. The NES-101 returned to the standard top-loading method, used by almost all cartridge systems before and since for its ease and reliability.