Ive been through this dance with every body since the 5D Mark II. Its totally frustrating how much they charge for some plastic and a few buttons. Over the years, I have tried a ton of third-party grips and some are definitely better than others. Right now, because the R5 II is so fresh, the market is still catching up, but here is what I found based on my testing...

• Canon BG-R20 Battery Grip for EOS R5 Mark II
• This is obviously the gold standard. In my experience, the weather sealing is the only thing that actually justifies the price. If you shoot in the rain or heavy dust, just bite the bullet and get it for the peace of mind.
• Vello BG-C18-2 Battery Grip for Canon EOS R5 R6 R5 Mark II
• Vello is usually my favorite alternative. It feels slightly more hollow than the OEM version, but the buttons are clicky and it fits the mount perfectly. I used their older version for years without any issues.
• SmallRig Mount Plate and Grip Extension for Canon EOS R5 Mark II
• If your main issue is just the size of your hands, this might be a better route. It wont give you the extra battery life, but it fixes the ergonomics without costing a fortune. If you really need that vertical shutter and the dual battery power, the Vello is gonna be your best bet. Just be careful with the battery tray, they can be a bit flimsy compared to the Canon ones. If you go third party, just make sure you are using genuine batteries in them, because sometimes the communication between a fake grip and a fake battery makes the camera act real weird. Reach out if you need more details on how the Vello holds up over time.

Regarding what #1 said about "Ive been through this dance with every body...", I am right there with you. Honestly, if you just need the extra bulk and better battery life without dropping five hundred bucks, I have been super happy with a mix-and-match setup that works just as well. I basically skipped the official grip and went with this combo instead:

• SmallRig L-Bracket for Canon EOS R5 II 4387 to give my pinky a place to rest and make the body feel way more substantial in my hand.
• Anker 737 Power Bank 24000mAh 140W which I just keep in a pocket or strapped to a tripod leg.
• Neewer LP-E6NH 2250mAh High Capacity Battery 2-Pack for quick swaps when I dont want to be tethered. The USB-C PD power bank trick is a total lifesaver for the r5ii because it actually keeps the camera topped off while you are shooting. Its way cheaper than the OEM grip and honestly more versatile for long days... no complaints so far.

> honestly fed up with this r5 mark ii dying halfway through my shoots. Like someone mentioned, the official grip price is daylight robbery. Basically, the group consensus is that third-party battery solutions are way more cost-effective. I love using the SmallRig 4734 Full Cage for Canon EOS R5 Mark II with a SmallRig 2093C Side Handle for ergonomics. Then I just plug in a Ugreen 145W 25000mAh Power Bank for 27W PD charging. It works perfectly and costs way less. Amazing stuff!