Allstar shoulder base is an Arri-style bridge plate. It was designed for F3, AF100, FS100...these lower height camera. You can get very low optical axis and center of gravity when doing hand-held shot.
It is made of 7075 aluminum and did hard anodizing for surface treatment to provide strong and wear proof surface. There are two LW 15mm clampers on both side, and it can be mounted on ARRI style dovetail that you can adjust the balance after changing lenses.