Heavy Duty Industrial Curtain Trolley with Four Steel Wheels. The double steel wheels on steel bodies are recommended for curtains weighing more than 100 pounds or over 15 feet tall. These rollers are compatible with the 16RT tracks. The steel plate provides a drop of 1.5 inch below the roller track, and offers a hole to accept chain, hook, or other fastening methods. Pull Rope Trolleys, recommended for curtains over eight feet tall. These trolleys are the strongest rollers we offer. Recommended for applications of extreme curtain weight or height. Hole diameter 0.38 in.