got out this morning for about 2 hrs,low tide just to try out the CZ21..it worked just as the CZ20 did..BUT it did tone Gold/Tab tone on about 1/2 of the crusted pennies (this i don't like!).......my GT would only do this about 1 out of 50! other than that i like it very well.depth was good ,about 12" on a penny..only falsed a couple times,and that was with sensitivity on 10! not bad.i will give her another go tomorrow!