yo, I went through this exact same dilemma last year. Ngl, I was sooo hesitant to drop the cash on the OEM, so I experimented with a few. First, I grabbed the Viltrox EF-EOS R Mount Adapter but the pins were sketchy and it kept dropping communication. Then I tried the Commlite CM-EF-EOS R Electronic Auto-Focus Mount Adapter. Honestly? It was amazing for the price. The AF speed felt basically native, but I noticed some play in the mount after heavy use. I also checked out the Meike MK-EFTR-A Auto-Focus Mount Adapter which is okay, but the build quality felt a bit "plastic-y". Technically, none of these have proper weather sealing, which is a HUGE risk for your sensor. Like the first guy mentioned, I eventually went back to the Canon Mount Adapter EF-EOS R just for peace of mind!

In my experience, I had issues with the Viltrox EF-EOS R Mount Adapter cuz the mount tolerances were off, messing with the 12-pin communication... basically a nightmare. Quick tips:
* Get the Canon Control Ring Mount Adapter EF-EOS R.
* It's the only one with legit weather sealing. Unfortunately, third-party build quality isnt as good as expected. i learned my lesson. gl!

Hmm, I've had a different experience than the others here. Ngl, the official Canon options mentioned are obviously top-tier, but if you're strictly looking for VALUE, I'd actually suggest looking at the Commlite CM-EF-EOS R Mount Adapter instead of the Viltrox. I know people worry about third-party reliability, but I've been using this one for two years and it’s honestly rock solid for daily work. Here is why I think it’s the better play:
* Build quality is actually all-metal. There is basically zero lens wiggle or that annoying "play" in the mount you get with some cheap stuff.
* Communication is flawless; it handles the AF and EXIF data perfectly without those weird "connection lost" errors that haunt the Viltrox.
* It costs way less than the Canon Control Ring Mount Adapter EF-EOS R but feels just as sturdy in the hand. Be careful tho, if you're always shooting in heavy rain, the OEM is still king for weather sealing. But for most of us? The Commlite is basically the same performance for a fraction of the cost. Definitely worth a look if ur trying to save some cash for more glass haha!! peace.

Im gonna respectfully disagree with the idea that its only Canon or bust for reliability. While the OEM gear is top-tier, I have been using the Meike MK-EFTR-A Auto Focus Mount Adapter for a long time now and it has been rock solid. I found the mount tolerances much tighter than the Viltrox options which really helps avoid those annoying lens connection errors when you are moving the camera around.

• Quick tip: Check the mount for any play or wiggle right out of the box. If it moves even a tiny bit, exchange it immediately because that is how communication errors start.
• Quick tip: Keep the electronic pins on the adapter clean with a tiny bit of isopropyl alcohol to ensure the AF communication stays snappy over time. Basically, if you dont want to drop the cash on the Canon version, this is the most reliable budget pick imo.

Just saw this thread. After using the R system professionally since launch, I've found that value shifts once you consider the utility of drop-in filters. If you shoot video or landscape, the basic adapters are honestly a bit of a waste.

• Canon Drop-In Filter Mount Adapter EF-EOS R with Variable ND Filter A: This is the gold standard. It's pricey, but the convenience of having a VND behind the lens is a game changer. The weather sealing is perfect and the glass is totally neutral.
• JJC EF-EOS R Drop-In Filter Mount Adapter: If the Canon price is too high, this is my pick for best value. It includes both a CPL and a VND filter for a fraction of the cost. The build isn't quite as robust as the OEM, but for daily use, it's surprisingly reliable. In my experience, sticking with the drop-in systems offers way more long-term value than the basic metal rings, even if you pay a bit more upfront.

Adding my two cents... I've been around the block with Canon for decades and I’ve tried just about every way to mount old glass to new bodies. While the others are making some good points about features, I'm gonna take a different stance. If you're looking for actual value, the basic Canon Mount Adapter EF-EOS R is the only way to go. I know it seems boring compared to a VND or a control ring, but over the years I've learned that simplicity is king. I once had a third-party mount basically crumble in my hands during a cold weather shoot because the metal was some cheap alloy. Since then, I’ve been a bit of a purist. The basic Canon one is rock solid and doesn't have any extra electronics or moving parts to get gunked up or fail. Tbh, you can usually find these used for dirt cheap because people upgrade to the control ring version. I've snagged a few that way and they never let me down. It’s the best way to ensure your EF glass actually performs like it’s native without any weird glitches or mount wiggle. Sometimes the most basic tool is the right one for the job, ya know?