I use Humminbird 899 di si hd so I know they are moving on me. I can see them good on the unit when I drop and mark them. I put most in the Illinois Bayou area, so I assume that it is current. Hadn't really thought if someone relocating them. I was putting one block per tree, so I guess I'll try two blocks this year. The few trees that stayed where I put them did provide me with a lot of fillets last spring !!