What size limitations must a custom-made top box for a motorcycle adhere to?

The correct answer stipulates that a custom-made top box for a motorcycle must not exceed the dimensions of 2 feet by 2 feet by 2 feet. This size limitation is crucial for ensuring that the top box does not create significant drag or imbalance, which could affect the motorcycle's handling and safety. Additionally, the requirement that it does not obstruct the side mirrors is vital for maintaining visibility, allowing the rider to see vehicles and obstacles behind them, thereby enhancing overall road safety.

Furthermore, the mention of needing to be LTO registered emphasizes the importance of compliance with local regulations governing vehicle modifications. Registration ensures that the custom top box meets safety and reliability standards set by the Land Transportation Office, which is essential for the legality of its use on public roads.

In contrast, the other options either suggest sizes that exceed the permissible limits or include requirements that could compromise safety or legality, such as obstructing side mirrors or not being LTO registered. Adhering to the specified dimensions and regulations helps maintain the integrity and safety of motorcycle use.