100% Polyester 3MM CLASSIC MESH WITH 85% LIGHT BLOCKING RATING: Constructed from 3 mm mesh with A.C.T. Air Channel Technology for unrestricted airflow. 100% polyester. 1" (2.54 cm) trim on top and bottom. Machine washable. FITS FULL-SIZE STYLES WITH A 52" x 28" (132 CM x 71 CM) MATTRESS: Install long 11" x 111" (28 cm x 282 cm) and short 11" x 82" (28 cm x 208 cm) panels to cover 4 sides or only the long panel to cover 3 sides. Do not use on solid end styles or mini cribs. SAFETY TESTED & TRUSTED: From BreathableBaby, the original breathable mesh liner with millions sold since 2002. Independently tested for safety to comply with ASTM F1917 for infant bedding. Contains no added chemicals, flame retardants or formaldehyde. HELPS KEEP ARMS AND LEGS SAFELY INSIDE WITHOUT THE RISK OF RESTRICTED AIRFLOW: A single layer of breathable mesh allows exhaled air to pass through the fabric and mitigates risks associated with padded "crib bumpers" (banned in the US in 2022). EASY TO INSTALL: Adjusts to fit with hook and loop. Tuck the bottom fabric trim below the top edge of the mattress and secure all fastenings before use. Review instruction manual and installation video or contact customer care for assistance.