Hatroi HA602 Steel Nut for #643, #644, YS4C-63 and OS4C-70 RC Fittings  [HA602]

Direct-replacement nut for RC fittings

This Hatroi HA602 nut is a scale RC replacement designed to fit the part codes shown in the product name: #643, #644, YS4C-63 and OS4C-70. It functions as a fastening component for model engines and associated fittings when the original nut is missing, worn, or being changed during routine upkeep.

Compatibility is limited to the codes listed, so confirm the correct part number on your model before ordering. The nut performs a mechanical role: it secures mating studs and fittings, keeps alignment, and helps limit vibration transfer that can influence idle stability and tuning consistency on small RC power units.

Installation is suitable for standard hobby workshop tasks. Clean mating threads, start the nut by hand to check correct engagement, then tighten it to a snug fit without over-torquing to avoid thread damage. After first installation, verify seating and recheck after a short test run as part of normal maintenance.

For setup and track spares, treat this nut as a basic service item: replacing worn fasteners prevents misalignment and erratic behavior, and carrying matching hardware speeds repairs at the field.