Transducer of the unit your viewing the 360 on is used if you want depth and temp settings when you use the 360. 360 is a transducer itself but it doesn’t give depth or temp readings. 360 setting used is 455 MHz and you get a good pic using it, my recommendation is viewing 360 on a 10 or bigger as I like using the 360 in “front view “ setting and not entire circle view on a 10 screen. I also like using fine/fast sweep over standard sweep setting. The larger Humminbird units 10 and 12 have more pixels per sq. Inch and will give a better detailed picture as well as you can use any mega transducer with the 360.