JZP-13.5-SC Rubber Shock Absorber: Standardised 60 mm Mount with Inspected Batch Quality Direct answer: The JZP-13.5-SC is a 60 mm rubber-to-metal isolator rated at 13.5 kg per mounting point, built to one fixed dimensional and compound standard so that every delivery batch behaves like the previous one. Mounting is an M5 thread with a Φ5.5 mm anchor hole, and resonance sits at 41.5±5 Hz with damping of 0.13 or higher. What makes an isolator easy to fit on an existing bracket