The AW & AWH models are recommended to be used immediately under most HVAC equipment and in conjunction with structural steel bases and concrete inertia blocks. Baseplates of all designs are factory drilled to accomodate Risk-free and effective installation of your spring mount into the composition or flooring. -OtherHVAC Equipment: https://cesardxrkc.blogunteer.com/37965981/the-2-minute-rule-for-hvac-spring-isolator