Some people think these are dumb and not needed.. and then they drop their guitar when the strap lets loose! These Flex Lock Strap Blocks from D'Addario are a hassle-free strap locking system designed for players who don't want to modify their existing end pins. Simply slip the Flex Lock Strap Blocks over your existing strap buttons and youre ready to go. Inspired by the classic Grolsch bottle cap strap lock solution. Pays for its self in their first use! • MFSKU PW-FLSB-04RD • UPC 019954392406