After a good two years of their new R series mirrorless cameras, Canon have still not produced their own RF extension tubes yet, so after some quick research I decided on these good looking Meike ones. They are well made with quality plastic/ABS barrels, metal mounts and gilt plated data pins, and are fully auto. They are weather sealed with a soft rubber seal at the rear mount, and the matt finish matches the non-L RF lenses exactly. The rear cap fits well enough, but oddly the front body cap is a loose fit and will not tighten up, and is best discarded. A surprisingly poor design but replacements are cheap enough to buy online.
The original description was for two tubes of 11mm and 18mm, but they turned out to be slightly better at 13mm and 18mm. A pity they weren't a full 3-part set giving a true 1:1 reproduction ratio. They also aren't supposed to work with the RF 35mm f/1.8 lens because of a projecting ridge on the rear of the lens, but mine actually worked fine with both tubes. With lenses set on manual focus and infinity for best quality, the two tubes produced an image of about double life size with the 50mm f/1.8 lens, and slightly better with the 35mm one.
Considering the tubes have no optics or circuitry in them they are not that cheap, but compared with some of the outrageous prices from other manufacturers for exactly the same thing, they represent good value. If you want to get into macro photography quickly and easily, these quality Meike extension tubes are the answer. Highly recommended.