Swarovski Optik STX Eyepiece Module Lightweight and rugged housing; Supple yet durable rubber armor Nitrogen-purged interior for waterproof/fogproof performance -13 to 131F (-25 to 55C) operating temperature; Submersible to 13 ft. (4 m) Click-stop twist-in (and removable) eyecup; One-handed operation via side-by-side zoom and focus dials SWAROCLEAN non-stick coating on ocular surface