TL Reefs Magnetic Locking Frag Rack, LargeThese frag racks will not disappoint! They will securely hold your frags in place, on aquariums up to 3 4" thick. FDA grade silicone locking layer holds plugs securely. Nothing will knock them out. Strong Neodymium magnets combined with a grippy oring hold the rack securely in place on aquarium thicknesses up to 3 4" Magnets are completely encased in cell cast acrylic and will never get water in them. No worries about rusting magnets causing water