M4 brass expanding inserts are used to create durable metal threads in plastic parts. They help plastic components handle repeated assembly and disassembly better than a direct plastic thread.

Reversed for through hole indicates the insert is designed for through-hole applications rather than a blind-hole layout. This style is chosen when the part geometry or fastening direction calls for that insert orientation.

Yes, threaded brass inserts like these are commonly used in 3D printed plastic parts when an M4 machine screw thread is needed. Final fit depends on the printed material, hole design, and installation method.

Brass inserts provide a stronger, more wear-resistant thread than plastic alone. They are useful when a part will be assembled multiple times or when a more secure machine-thread connection is needed.

Choose an M4 insert when the fastener size is M4 and the plastic part is designed for an insert rather than a cut thread. The flange and through-hole design should also match the part geometry and the required retention method.