Protex WDC-160 Protex Wall Drop Box w/Adjustable Chute Drop opening 1" thick and 8-1/2" wide, thick enough to drop keys The perfect way to lock and secure keys, mail, car remotes, small envelopes and more Recommended wall thickness for proper installation is between 5 to 8 inches. Tubular-style key lock with Double "D" configuration (can be retrofitted with other cam locks) Chute is adjustable for walls between 3-D/4" - 7-3/4" thick. Interior Dimensions: 11-3/4 (W) x 10 (H) x 5 (D) inches Indoor use only.