WHEN THE CHANGER IS ROTATED, WIRE LIFTS SUCTION CUPS EDGE, CAUSING LETTER TO RELEASE. Fast-Ad changers are available in the following sizes: 1.750 Cup for 6" and smaller letters; a 2.5" Cup for 6" and 8" letters; a 4" Cup for 8" and larger letters. For letters larger than 15", a Double-Head Changer is recommended. For very large pricing numerals, an Extended Double Head (cups are spread wider than standard double-heads) is available. Extension poles come in 12', 18', and 24' lengths.