The smaller Magmounts (about 10mm in diameter x4) are geared towards the aquarist who wants to attach corals to their existing rock structure (one Magmount is attached to the coral or rock rubble while the other it attached to the structure).
The medium size Magmounts (about 20mm x2) are for mounting corals/rocks/frags/powerheads etc. though a pane of glass. One Magmount is placed on the outside of the aquarium while the other is attached to the coral/frag/rock etc on the inside of the aquarium.
The eXtraLarge Magmount is used to mount heavier rock/powerheads etc or for larger aquariums where thicker glass is involved.
The Magnount plates can be used in miscellaneous applications or to build a thin Magnetic Cleaner to reach areas that can't be cleaned with standard Algae Magnets.
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