I recommend reading this one — Breakthrough always supports its claims. Also, be sure to compare prices.
From Breakthrough Filters:
“Breakthrough R” Drop-In Filter System for Canon R-series cameras.
San Francisco, California – Breakthrough Filters today unveiled a new drop-in filter system called “Breakthrough R”, comprising 27 filters designed specially for Canon R-series cameras, such as the Canon R5 and R6. Every filter manufactured by Breakthrough Filters is now available as a “R” drop-in filter, including a number of all-new filters such as the world's first Variable ND which covers 2 to 11-stops, without an "X Pattern", Black & White Polarizers and Infrared.
“Breakthrough R” Drop-In Filters feature a rugged, weather-sealed construction designed to withstand the elements with dust and water resistance. And to make identifying filters fast and easy, each filter is color coded. Multiple “Breakthrough R” filters are easily stored in an all-new compact travel friendly cases that fits up to 5 filters. And an improved, larger adjustment wheel makes fine tuning polarization smoother than before.
Largest Selection of Drop-In Filters
The new “Breakthrough R” Drop-In filter system has a wide range of 27 filters to choose from – Neutral Density, Polarizers, Dark CPLs, Infrared, Night Sky, VNDs and Black and White Polarizers.
X4 CPL Performance: Highest Transmission, Lowest Color Cast
Performance is critical to pros, whether they’re shooting detailed landscape images or 8K video. The X4 CPL is the most color neutral polarizer, with an unrivaled light transmission of 50.24%.
When compared to industry leading filter manufacturers of both circular and drop-in polarizers, the X4 CPL R ranks number one for light transmission and color cast performance, followed only by the Canon Drop-In CPL at 43.06%.
The result of a higher light transmission is faster shutter speeds, which can translate into sharper images and the ability to use a lower ISO when shooting video.
X4 Neutral Density Performance: Sharpest and Most Color Neutral ND Filters
Canon does not currently offer solid ND drop-in filters, however, optical performance of the X4 ND exceeds industry leading manufacturers such as Singh-Ray, B+W, Lee and many others. The X4 ND has the most neutral color transmission throughout the visible range and well into infrared.
X4 ND R filters are available individually or as part of a set and come in 3, 6, 10, 15 and 20-stop densities.
Dark CPLs, Night Sky and Infrared
Breakthrough Filters is announcing a number of other “Breakthrough R” filters available for pre-order, including Dark CPL R in 3, 6 or 10-stop densities. The Night Sky R drop-in filter eliminates artificial light pollution between 570 and 610 nanometers within the visible light spectrum and the Infrared 720 R drop-in Infrared filter cuts visible light up to 720 nanometers.
Breakthrough VND-R: World's Largest Density Range
Breakthrough Filters is announcing a VND filter system with the largest density range of 2 to 16-stops, which comprises two filters: VND-R and Dark VND-R.
The VND-R is the first Variable ND to feature 2 to 11-stops in one filter – without the "X Pattern". The effective density range of the Dark VND-R is 10-16-stops, with one stop of overlap between VNDs.
To limit the negative consequences of the "X Pattern" caused by cross-polarization, brands of Variable ND filters make numerous VND filters, each with a small density range, thereby requiring numerous VNDs to cover a large density range.
For the first time, the VND-R Filter System allows photographers and filmmakers to make exposure changes faster and more conveniently without the need to constantly change filters.
Comparing color and transmission performance of the many Variable ND filters on the market, the Canon Drop-In VND performs impressively, easily outperforming every Variable ND on the market for color cast and overall transmission performance, ranking second only to the Breakthrough VND-R.
Even on super-wide lenses such as the Canon 11-24mm, Sigma 12-24mm, Tamron 15-35mm, the VND-R and Dark VND-R perform exceptionally well without any visible "X Pattern".
The VND-R and Dark VND-R are available for pre-order individually or as a "VND-R Set".
Black & White Polarizers
In Black & White photography a circular polarizer is often stacked with colored filters, however with the all-new Black & White Polarizers the photographer is able to achieve the same result with a single filter.
Yellow, Red, Orange and Green Polarizers can be purchased individually, or bought as a set, and is available for pre-order.
Pricing and Availability
Watch for this: Breakthrough Photography will soon be introducing a weather sealed EF to RF Drop-In Filter Mount Adapter.