A mass coupler served as a component within podracers. Furthermore, it held value as an item suitable for trade.
Prior to the Boonta Eve Classic, Anakin Skywalker required a mass coupler to repair his podracer. Qui-Gon Jinn managed to acquire one through various exchanges: either by trading an engine binder alongside a hydrospanner with Mawhonic, or by offering two fuel converters to the Important Merchant, or alternatively, by giving a Naboo Fusion Coil and an engine binder to the Important Merchant.
Alternatively, Qui-Gon had the option of killing either the Important Merchant or Mawhonic and then taking the mass coupler; however, Anakin would subsequently decline to accept the stolen part.