Metal,6pcs,One size fits all (kids AND adults), quick to install, easy to use. SCIENTIFIC DESIGN: Shoe laces feature a unique curved magnetic buckle and flat elastic rope design. The magnetic and snap-on double-lock design of the lock makes you never worry that your shoelace will loosen; SCIENTIFIC DESIGN: Shoe laces feature a unique curved magnetic buckle and flat elastic rope design. The magnetic and snap-on double-lock design of the lock makes you never worry that your shoelace will loosen; The lace locks are curved that blends perfectly with your feet to keep your feet comfortable all day. PERFECT FOR EVERYONE: no tie elastic shoelaces are a great gift for seniors suffering from arthritis or other disabilities, autistic children, runners looking to speed their triathlon transition up, and a must for sports enthusiasts.