Decent HDMI to Composite converter

[Electronic M]

The plastic ones including the RF output models are mediocre and whether they even work in monochrome as received is a toss up.

The Best I found are a discontinued metal case variety that I wish I had bought more than one of back when Amazon carried them (I haven't had good luck finding used ones either).

Of course if letterbox bugs you all those boxes don't fix it on some sources like newer rokus...my solution to letterboxed HDMI is to get a HDMI to ATSC modulator (expensive... like $300 used expensive) and a 2009 vintage Zenith DTT-900 or 901 DTV converter box (or the LG or Insignia rebadged versions) with a zoom button on the remote (let's you choose between letterbox, 4x3 cropped from the center of a 16x9 image, or 16x9 horizontally squeezed into a 4x3 image) that's also accessible through the menu if you're using a universal remote.