Definitive in-ceiling di 5.5R speakers feature near-invisibility thanks to their small diameters, hidden flange design, and low profile micro-perf grilles. They are as easy to install as traditional flanged flush-mount speakers, and don’t require custom sheetrock/spackle skills to install yet they are practically invisible. The di 5.5R grille is a mere 7-3/8 inches (18.62 centimeters) in diameter, about the same visible size as competitive nominal 5-1/4-inch in-ceiling speakers.