Green crystal look japa counting beads.
Just tie them on your bead bag. Each bead represents one round chanted. Pull the bead down for each round to keep track. There are 20 beads. The first 16 beads are for 16 rounds, the other four beads are for every set of 16 rounds. For example, one bead equals one set of 16 rounds, the second bead equals the second set of 16 rounds or 32 rounds and so on.