Size 21 is Compatible with - Swarovski EL (2013 & Older), Swarovski SLC (2013 & Older), Sig Sauer Zulu6 HDX, Sig Sauer Zulu6 HDX Pro, Kite Optics APC Requires the Snapcase - Magnetic digiscoping technology instantly connects the Bino Adapter to Snapcase (sold separately) no more missed shots from alignment issues or complex mounting setups Always Ready in the Field: The embedded magnetic array provides a seamless and effortless method to mount your phone security to your binoculars with patented self centering design Built for Adventure: Compression fit design makes it easy to install when you want to utilize it and remove it when done, constructed from durable ABS plastic for resistance to outdoor conditions Connect, Capture, and Conquer: Transform your hunting and wildlife observation with the OLLIN Snapshot system, capture trophy animals and outdoor moments with unparalleled ease and image quality Transform your binoculars into a powerful digiscoping platform with the OLLIN Snapshot Bino Adapter, featuring innovative magnetic auto-centering technology that instantly aligns your smartphone camera with your optics for perfect shots every time. Built with durable ABS plastic and designed for permanent compression-fit installation, this adapter works seamlessly with all Snapshot Snapcases (sold separately) and is compatible with major optics brands including Swarovski, Vortex, Leupold, and Kowa. Perfect for hunters, wildlife photographers, and birdwatchers, the system allows you to transition from spotting to capturing in seconds, while the included magnetic protective cap ensures you're always ready to document once-in-a-lifetime wildlife encounters without missing a moment.