This is Agency Power AP-BRP-X3-500-BLK Battery Tie Down Bracket Can-Am Maverick X3 2017+. Manufactured by Agency Power.
Replacing the battery in your Can-Am Maverick X3 can be a daunting task. Moving the seat forward only gives you so much room to work comfortably and typically requires removing the seat altogether. Removing the plastic tie-down is just as difficult due to the multi-piece design. The factory battery tie-down also limits owners to which battery they choose to run. Owners are typically running higher output stators and batteries to permit the additional power draw from auxiliary accessories.