A transducer is the part of the fishing rig that uses sonar to detect where fish are beneath the boat. The best fish-finder transducers for you will depend on the gear you already have. When shopping for fish finder transducers online, you'll need to be sure to match the brand, frequency, and wattage to the fish finder rig you already have! If you don't, it won't fit or work correctly. Luckily for you, finding marine transducers online is easy with ReelTrail. Here you can buy, sell, or simply browse all the fish finders, fishing equipment, and other outdoor equipment you need. ReelTrail.com is the marketplace for outdoor enthusiasts to buy and sell new, used, vintage, and handmade gear online. Welcome to the ultimate website for outdoor gear and adventures.