Caputron Amrex Style Electrodes are comprised of a sponge with a metal mesh backing, all enclosed within a rubber casing. The smaller 2 x 2 Caputron Sponge Electrodes allow for more precise targeting. 2×2 is the smallest recommended size for tDCS electrodes. Be sure to combine this product with the Caputron Universal Strap, exclusively from Caputron Medical.