Amazon Returned Equinox 800 Metal Detector two coil Bundle, Pro-Find 35 Pointer with Minelab Gear
Most metal detector coils are not interchangeable between different brands or technologies. This is because specific brands and models have their own proprietary technology, different plug in connectors, and shaft attachments. Additionally most detectors operate at different frequencies and use completely different circuit boards. But, most brands and models will have different coil options for their metal detectors. And there are a few aftermarket coil manufacturers that make coils for specific brands too. The variations in coils will typically be in size or configuration.
Some metal detectorists like to use large coils to expand their search area to cover less ground quicker. These large coils also help the metal detector obtain more depth. On the other end of the spectrum are those who prefer to use a smaller search coil. Smaller coils help you detect more effectively in sites that are trashy or have a lot of vegetation growth. They detect less area and depth and make it easier to pick through trash targets to pinpoint more valuable targets.
The two most common types of coil configuration is the concentric coil or the double-D coil. A concentric coil has two coils. One large one and one smaller one. One sends a signal and the other receives it. This type of coils has a bowl shaped detection field.
A DD's two coils are staggered or offset. This creates a narrower search field...kind of a slice if you will.