They're 18mm headed bolts. I just finished mine yesterday. I've had the truck nearly 1 year and about 3 weeks ago I found that anything I had stored under the rear seat was wet and getting mildly moldy. We'd had a TON of rain the last couple months. Suspected my cab vents and since they're only $28, I went ahead and bought new ones. Found that a couple of my seat bolts were rusty enough to give me problems coming out, some PB Blaster and a wire brush from underneath and working them in and out a few times got them out with no issue.
I did find that putting the vents in is alot easier if you simply turn them 90* before trying to stick them through the hole. Most people say to put them through at an angle and that just wasn't working and I discovered the 90* trick.
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Did a water test and found I still had some issues. Looked to be coming from either a stopped up slider drain or the driver's corner of the back glass seal. Pulled the little retainers for the glass cables and found the drain holes. Pass side was fine, driver's side was full of gunk and I couldn't even find the drain holes to start with. Cleaned it all out, blew them all out with a WD40 nozzle and 120psi, fingers crossed that fixes it. Did the back seat mod as well so I can keep an eye on it going forward. Haven't done a water test again, wanted to enjoy a dry interior for a few days at least
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