Anschutz Spirit Level 6930 M18-It is used to eliminating angular deviation,vertically & horizontally. -It helps to improve accuracy. -It is also called a Bubbles. -This spirit level is useful for controlling rifle cant – Easy to use and install-The level can be adjusted without the use of tools and fits the M18 front sight perfectlyContact us at 70822-33324, if the product is in pre-order status.