A “BOM” (or “Bill of Materials”) is typically a list of all the parts that go into making something. Some racers list all their parts, which is awesome because it serves as a shopping list (with prices) of what you might need to build a car, and it serves as a record of what it cost someone to build their car and stay within the $500 budget. (Remember, the $500 budget does not include the original ride-on toy vehicle or the safety items used on the car.)