I use a couple of those cold crash guardians. They work well enough, but it is not possible to make sure all oxygen is out of the device as there is always some space left in the bag and hoses. I figure after a few flushes though it is good enough.
Off topic question though. I usually cold crash to 33F for a few days. I get some suck back as the temperature drops and the balloon deflates some. But after a couple of days at 33F I will get a lot more suck back. I can’t quite figure out what’s going on. I have checked the device many times and it free flows back out of the bag with no issue. And the temp is monitored by the Tilts so I am reasonably sure of the temperature of the beer.
Off topic question though. I usually cold crash to 33F for a few days. I get some suck back as the temperature drops and the balloon deflates some. But after a couple of days at 33F I will get a lot more suck back. I can’t quite figure out what’s going on. I have checked the device many times and it free flows back out of the bag with no issue. And the temp is monitored by the Tilts so I am reasonably sure of the temperature of the beer.