Neem wood means wooden beads with carved Sanskrit Hare Krishna Maha Mantra.
Sixteen for chanting sixteen rounds and extra four for chanting each set of sixteen rounds. Tie it onto your bead bag string and bring one bead down for each round of Hare Krishna Maha Mantra (108 Japa).
Hare Krishna Hare Krishna Krishna Krishna Hare Hare
Hare Rama Hare Rama Rama Rama Hare Hare