Garrett AT Pro Coil Compatibility Chart: Which Coils Fit and What They Do

Every coil below is listed by its manufacturer as fitting the AT series or the AT Pro specifically. Always check the exact variant at the point of purchase, because some aftermarket makers cut machine-specific versions of the same coil.

Separation and control. A 5 by 8 illuminates a smaller volume of ground, so when a dime lies four inches from a nail, the coil can see them as two objects rather than averaging them into one confused signal. It also fits between tree roots, along fence lines and into the corners of old foundations where an 8.5 by 11 simply will not go. The trade is coverage, and covering a large field with a small coil is punishing work. The coil coverage calculator puts a number on that penalty before you commit a weekend to it.

The other effect people underestimate is that a smaller coil usually runs more stably at higher sensitivity in mineralised ground, because it is averaging less hostile soil at any moment. On a hot site, the 5 by 8 can end up effectively as deep as the stock coil despite the smaller footprint.

Open ground with low trash, and large targets. The NEL Hunter 12.5 by 8.5 Coil for AT Pro covers noticeably more ground per sweep and reaches deeper on big objects, which suits fields, pasture and dry beach. Its own listing notes that it copes well with high and medium soil salinity, which is one of the few honest advantages available to an AT Pro owner working a beach, though it does not turn a single frequency machine into a salt machine. That limitation is set out in full on the settings by site type page.

The costs are real: more weight on the end of the shaft, more masking in trash and a larger pinpoint footprint, which means bigger holes unless you carry a pinpointer such as the Garrett Pro-Pointer AT. On weight, the AT series weight comparison is worth reading before you hang a large coil on a machine you already find heavy.

Mechanically and electrically the AT series coils share a common fitting, and Garrett sells the 5 by 8 and the stock 8.5 by 11 across the line, with the Mars Sniper listing naming the AT Gold, AT Max and AT Pro together. What does not transfer is behaviour. The AT Gold runs at a higher frequency aimed at small gold, the AT Max at a different frequency again, so the same coil produces different sensitivity to small low conductors on each machine.

Aftermarket coils are where care is needed. Some makers produce separate versions per model, and a coil described for the AT Pro is not automatically the right stock number for an AT Max. If you own more than one AT machine, the practical approach is to keep the coils you swap most often on the machine they were bought for, and check the AT Max settings before assuming a favourite park setup carries across.

Look at the ground, not the catalogue. Dense trash, old house site, anywhere you can see bottle caps on the surface: fit the 5 by 8. Open pasture, ploughed field, dry beach: fit the biggest coil you own. Mixed ground where you want one coil for the day: the stock 8.5 by 11 remains a sensible compromise, which is why Garrett ships it.

Whatever you fit, re-run your ground balance after the swap and re-check your buried test targets, because the same soil reads differently through a different coil. That interaction is why the depth ranges on the AT Pro depth chart are quoted against a specific coil, and why anyone quoting a depth without naming one is guessing.