Received the Ultimate 13" coil today. Air test shows about 1" increase in depth over the Fisher 11" coil on higher conductive targets like a dime and a quarter. On the lower conductive nickel and large gold ring, the increase was 2". I was testing in the garage and EMI only allowed me to run the gain at 80 with both coils. I weighed both the 11" coil with a lower rod and the Ultimate with an identical lower rod, results show the Ultimate weights 5.4 ounces more than the Fisher coil, 17.4 oz. vrs. 22.8 oz.. Though the Ultimate coil is a 13" diameter coil, it has a dip in both the front and back edges so lengthwise it only measures about 11" between these dips and the coil detects at depth only between these two points. At first glance, I thought the coil would only detect about the same length of coverage as the stock 11" coil but testing shows that the 11" coil doesn't detect at depth out to the ends of the coil either and it only actually detects at depth over about a 9" length, so a guess you still get about an additional 2" of coverage on each swing. It doesn't sound like much but it's about a 20% increase. I bought this coil because I thought it may work out to be a great coil for dry sand beach hunting. I have to wait a couple of weeks to give it a true field test. Stay Tuned.