I just installed this and unlike many reviewers, I DO come back and do updates on my reviews as I spend more time with the product.Before buying this (or any cover) go check out the demo AND install videos on Real Truck. I wouldn't necessarily buy from them but its a good reference resource.I did a ton of research before buying this cover. I wanted something flush and NOT VINYL (anyone putting a cheap vinyl cover on a 50k+ truck needs to take a look at their priorities). I decided on a flip hard cover due to my typical use. One very important thing to take into consideration is whether you need to lift the back of the cover before closing the tailgate - many of them require it, such as all of the Gator hard covers. The regular UnderCover Flex also requires this, as do the cheaper BAK covers. Just give a hard no to any cover that requires you to lift it before closing the tailgate - that's just total nonsense.I picked this cover due to the ability to fold to the cab, better build quality over the BAK F1 or MX4/GM Rev (MX4/GM Rev are the same cover), and got a good price on it. Otherwise I would have went with the ACI Lomax / Weathertech Access, which are identical covers and probably the best quality of all of them.ALL of these covers, regardless of brand, say they are not 100% weather tight and act like that's impossible. No, it is BS and it's because they are too cheap to design a weather tight cover, though happy to price the cover as if it was. My previous trucks were a 1st Gen Chevy Avalanche and 2nd Gen Escalade EXT, which use identical factory hard covers and they are weather tight and super durable. There is nothing in the aftermarket like them and they only fit on those trucks.Anyway, back to this cover. Installed on my '18 Sierra SLT Crew Cab, short bed. It has the factory spray in bed liner. The instructions for the cover are actually for the Flex and not the Ultra Flex. That doesn't really matter other than the mentioning of having to open the cover, which isn't required on the Ultra when closing the tailgate. The clamps for the GM trucks are different than the Ford and Ram stuff, as they are black instead of the bare metal ones and the supplemental instruction pack mentions that. The back brackets are also different, as you have to install the back through the rear pockets and pop out the rubber round knock-out to run the bolt through it. Super easy to do. The videos don't mention how much to torque the bolts to, but the instruction mention 70 inch/lbs, which is what I set them to.The rails go in easy and fit well. The instructions do NOT mention the roll of weather stripping. Neither does the Ram install video on Real Truck but the Raptor video does show it. You put it at the front of the bed near the cab and it is the cheapest weather seal you could possibly buy. It's the discount crap that you get at the hardware store. I'll eventually upgrade it though luckily it isn't seen unless the cover is removed. Install of it is easy.The instructions do a poor job on mentioning the routing of the drain tubes. On my Sierra, there are three oval knock-outs at the back of the bed. I popped out each of the outer ones, and using a stepped drill bit, I made the hole just big enough that the tube tightly goes through it. This made for a clean and secure fit and took about 5 minutes to accomplish...this is the proper way to do the drains on this truck.Putting the cover on is easy as well. The newer design for the bolts that attach the front of the cover have them stay together as a full assembly, which is an improvement over the video. Just line it up, tighten it and you are good to go.I put this on in the garage with the bed wet (I did sop it up with towels). It has rained a bunch since and I keep the truck outside. I found a little water in the bed, but I can't tell yet if that is residual or leaked through. I can tell water will get in if rain is blowing toward the tailgate, as the back of the cover does a poor job at the corners sealing to the tailgate (by design).I still need to install the soft tool box, as I ran out of time and will need to do a little tweaking to get it exactly how i want it. I'll probably pass on the lights as the bed is already lit from the factory.I will update as I have more experience with this cover.11/19/18 Update: Yep, she seems to leak a bit. Mostly coming from the back of the bed and more on the passenger side. I am betting it is from those two areas where there isn't really a seal at the corners of the tailgate.The soft toolbox is installed. I was able to get it where I have full clearance to the bed hooks. It is not waterproof by a long shot and can't hold heavy items, but is still a nice feature.I ended up installing the bed lights. I mounted the controller high and tight to each rear bracket, so it looks semi stock. Wire runs through the factory wire pass through area and the lights are mounted under the UltraCover bed rails. They do a decent job lighting up the bed. I decided to mount them because in GM's infinite "wisdom" they require the bed light switch to be turned on inside the truck to light the bed with no other turn-on option. Not the least bit useful - my last truck unlocking it would turn on the bed light. I'll likely end up using these more than the factory lights.