1、Secure Protective: The internal thread design can be screwed directly on the lens mount thread to protect the lens more securely. 2、Durable Construction: Made from high strength aluminium alloy, these lens covers are built to last, withstanding the rigors of outdoor use in various weather conditions. 3、Wide Application: Suitable for M54x0.75 size astronomical main mirror or photographic sleeve with M54 external thread. 4、Easy to Use: The threaded design allows for quick and effortless installation, ensuring hassle free operation when covering and uncovering your telescope eyepieces. 5、Sleek Design: The black finish of these dust caps adds a touch of sophistication to your telescope setup, giving it a sleek and professional appearance.