I rented a clamp-on ultrasonic flow meter (Flexim) last week to commission a 3" DHW recirc loop and was able to drop the pump VFD 22% after verifying flow, which cut kWh and stabilized return temps. For those using these routinely, which models have given you reliable low-flow accuracy on steel and copper, and how do they hold up on insulated pipe when we’re chasing sustainable water-side tuning?