Polymeric interphase insulating spacers are designed for the insulated fixation of conductors in overhead power lines (OPL) with voltages ranging from 10 kV to 220 kV. They operate at ambient temperatures from -60 °C to +50 °C and are installed at altitudes not exceeding 1000 meters above sea level, in areas with pollution degrees from one to four according to GOST 9920.

The spacer's construction includes a fiberglass rod providing mechanical strength and a protective sheath made of silicone rubber, which shields the rod from atmospheric effects and increases the leakage path length. Metal end fittings ensure the connection of the spacer with conductors and OPL support elements.

Spacers are classified by the following parameters:

• Design type: interphase insulating spacer (RMI).
• Nominal voltage: from 10 to 220 kV.
• Mechanical breaking strength in tension: from 16 to 70 kN.
• Structural height: from 0.4 to 6.0 m.
• Clamped conductor diameter: from 9.6 to 46.0 mm.
• Type of end fittings: depending on the conductor diameter (A, B, V, G, D).

Example of designation: RMI-16/35-2.5-A, where:

• RMI — interphase insulating spacer.
• 16 — mechanical breaking strength in tension in kN.
• 35 — nominal voltage in kV.
• 2.5 — structural height in meters.
• A — index corresponding to the clamped conductor diameter (9.6–15.2 mm).