Breakthrough Filters X4 CPL Filter 77mm Purchased through personal import from the US official website. (149 USD) ※ I am also listing other types of filters, so please take a look. Below is a translation from the official website: The X4 CPL is designed to be the sharpest and most color-faithful polarizing filter on the market. Utilizing our own developed CPL film, cutting-edge coating technology, and a precision-machined brass traction frame, the X4 achieves unparalleled performance and durability. The world's most color-accurate CPL filter. At the core of the X4 is a brand new, in-house designed CPL film manufactured in the USA. While many manufacturers use off-the-shelf polarizing film for LCD panels, we have developed a unique approach specialized for optical precision. The X4 CPL uses ultra-high transparency SCHOTT B270® optical crown glass made from the purest raw materials, and is further treated with state-of-the-art MRC16 and nanotec® nano-coatings. As a result, we have created a CPL filter with the highest light transmission currently available, achieving incredible sharpness and color fidelity.