This ARRI R2 138mm Filter Ring fits into the back of ARRI matte boxes with a rear opening of 143mm. It enables mounting a 138mm round filter, such as a polarizer, onto your matte box and allowing for rotation of the filter. The R2 ring acts as an anti-refection donut and supports lenses with a front outer diameter of 114mm, such as Master Primes, Ultra Primes, and LDS Ultra Primes. It will accept optional R4 reduction rings, allowing you to use select lenses with a front outer diameter of less than 114mm.
For matte boxes with rear 143mm opening
Anti-reflection donut accepts 138mm round filters
For lenses with a 114mm front outer diameter
This R2 ring works with both internal and external focus lenses, as it is flexible and can accommodate the expansion and contraction of external focus lenses
Accepts R4 reduction rings for working with lenses that have a smaller front outer diameter than 114mm