The 16-204 kit uses very small #4-40 screws that fit nicely through the corner holes in the Hydromat. These are generally the right answer for the smaller Hydramat installations on steel tanks. The larger (heavier) Hydramat (15x15 or larger) should use the Hydramat Magnet Kit, 6-32 Magnets. Likewise, when installing in an aluminum tank it is best to use the larger 6-32 magnet kit and it is necessary to add the 16-205 Disk Magnet Kit on the outside of the tank.
The HydraMat magnet kits are designed as a cost effective solution for mounting the Holley HydraMat in the fuel tank or cell. Ideal for use in fuel tanks with a small sender opening where the Click Bond kits cannot be used. Once installed, the magnets can be positioned so the HydraMat lays flat in the bottom of the fuel tank.