This is one of three required pieces for digiscoping with the Impact system. In addition to the phone phone block, you will need a phone adapter and an eyepiece adapter.
The phone block serves as a base to align the adapter to the phone camera(s). The standard versions are semi-permanently attached to a phone case with adhesive. The MagSafe phone blocks attach using the built in magnet in most iPhones.
The standard block will work on just about any phone but only allows for alignment to a single lens. The Pro Phone Blocks allow use of both the regular and telephoto lenses. The configuration of lenses determines the shape of the block so the footprint on the phone will vary from block to block.
The setup video here shows how it works in a little more detail.
