Sachtler Ace Matte Box

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You can buy a matte box for $20 or even McGyver one up yourself out of cardboard and duct tape; you can also spend $5,000 or more. At $477 for the Ace ($1,350 for the whole kit including matte box, base plate and follow focus), you're getting a  thoughtfully engineered set of compromises that work beautifully with mirrorless and DSLR cameras, right on up to Sony FS5/FS7, Canon C100 Mk II/C300 Mk II or Blackmagic cameras. I think it's a great piece of kit. But with this written, make sure those compromises work for you: high-grade plastics instead of metal; a single, partially rotating filter holder instead of two full rotating holders; and the absence of height adjustment of the matte box itself - Sachtler leaves that to their base plate, which I think is fantastic. It works perfectly as an ensemble piece, but even then some cameras (like the FS5) locate the lens mount high enough above the camera's base that the lack of height adjustability of the 'box becomes an issue.  Make sure you try it with you gear first -- or make sure that whoever you buy it from has a good return policy.