The Halo's are awesome just apply a double sided tape or a adhesive in about 4 spots on tank rim before putting on Halo so it keeps it secure and in place. They put enough lift on tanks to keep from smashing the sensors and they protect the tank ring from getting scratched or gauged n rusty. They are perfect. I took and cut a piece of corrugated plastic into a circle the exact size of the inner Halo ring and I push that to make a cover over the tank sensor to protect it from weather and from it falling off or being shifted around accidentally when my tanks are being filled. I've been doing this for about 4 years now and still working perfectly.