Flat magnet wire is useful in products such as voice coils in loudspeakers, field and armature coils in rotary and linear motors, and transformers, in which the flat wire permits more compact coils and improved heat dissipation, as compared to designs based on round wire.

For a chart on the Insulated Flat Wire Sizes - Insulated Flat Wire 11 - 32 AWG Ratio Chart

The wire is produced from round, pre-insulated wire, which is then flattened. This flattening causes only negligible stretching, so the cross sectional area is the same before and after the process. Therefore the insulation is stretched in only one direction, and the resistance and wire gauge remain largely unchanged.

Flat Magnet wire is available with these types of insulation:

Solderable Polyester - 180° - Polyester / Polyamideimide / Bondcoat. Heavy Build. UL recognized.
Polyester A/I Topcoat - 200° - Polyester / Polyamideimide. Heavy Build. UL recognized.
Aromatic Polyimide - 240° - Polyester / Polyamideimide. Heavy Build. UL recognized.

180°C Bondable - Only certain AWG sizes have this insulation available.
200°C
240°

Information on Tinned Copper Wire