Quick question - how bad is your weather? Canon BG-E21 Battery Grip has pro seals while Vello BG-C16 Battery Grip for Canon EOS 6D Mark II is a budget build. tbh, OEM usually wins.

TL;DR: Don't trust the cheap $50 options for weather sealing—I tried the Vivitar VIV-PG-6DII Multi-Power Battery Grip and it failed me in the field. Story time: I went through this last year. Ngl, I was trying to be budget-conscious and grabbed a Neewer Vertical Battery Grip for Canon EOS 6D Mark II for around $50 instead of the pricey OEM. Unfortunately, it was not as good as expected. The technical specs claimed it was solid, but the shutter button felt like mush and I had issues with the communication between the grip and the body... it kept throwing "Err 01" codes. Plus, the gaskets were sooo thin. I really wanted to save that $150 difference, but it just didn't hold up in the humidity. It's great for indoors, but for weather sealing? Highkey disappointed. I guess sometimes you get what you pay for... gl!

> The official Canon BG-E21 is an option, but are third-party brands like Vello actually dependable? Yeah, honestly, I spent way too much time looking at the contact pin schematics for these. I'm kind of a beginner at fixing my own gear but I love the technical side of it. Basically, if you do go with a third-party like the Phottix BG-6DII Premium Series Battery Grip, you might notice the rubber seals aren't as tight as the OEM one. I actually tried a little DIY fix on mine using a tiny bit of silicone grease on the battery door gasket to help with the moisture. It sounds realy weird but it helped! Just be careful not to get any on the electrical parts. Also, for the 'Err 01' stuff people mention, I found that just cleaning the contacts with 90% isopropyl alcohol and a Q-tip every few months makes a huge difference. Has anyone else tried doing their own self-service or maintenance to save some cash instead of sending it to a pro shop?

Saving this whole thread. So much good info here you guys are awesome.

Warning: dont trust cheap seals!! I used a budget grip and it *realy* leaked. 1. Poor gaskets.
2. Pins fail. Consult a pro shop, but official is amazing! Stick with that.

So I’ve been through this whole "OEM vs Third Party" rabbit hole multiple times over the last decade of shooting EF glass. Honestly, when I was doing heavy field work, I did a deep dive into the actual manufacturing specs of these grips because I was tired of gear failing in the humid environments I usually shoot in. * Canon BG-E21 Battery Grip: The internal chassis is reinforced and the communication pins use a specific gold-plating thickness that handles high-frequency data much better. I never had those weird communication dropouts with this one.
* Meike MK-6D2 Vertical Battery Grip: This is a decent mid-tier alternative. The tactile feedback on the dials is actually quite clicky, but the gaskets are standard rubber O-rings rather than the custom-molded seals Canon uses.
* Vello BG-C16 Battery Grip for Canon EOS 6D Mark II: It's solid for studio work, but I found the polycarbonate shell flexes slightly when I’m using heavy L-series telephotos, which can actually break the weather seal contact temporarily if you’re not careful. I basically realized that if you’re torqueing the grip with a heavy lens, that body-to-grip flex is what compromises the sealing more than the rain itself. Definately something to keep in mind if you're shooting professionally tho!