I bought these for my mom and sister, as they seem to travel solo a lot. They are very small and weigh almost nothing, but high quality. Very easy to install and keep the door lock secure.

I use this in my balcony door for my peace of mind. It's very simple to use and seems effective.

This is a great concept! But could have been designed better. In the past, I've used duct tape to accomplish the same thing. I take a long strand of duct tape, roll it length-wise into a tubular shape with the sticky side out, then twist the duct tape into a rope like chord, and then strapping down the dead bolt to the door knob by wrapping it around in a loop, and being sure to tug down on the deadbolt in the locked position (see photos) I had even considered creating a similar product this one.
But this product has a design flaw, at least with regards my particular dead bolt. My deadbolt is flush up against the door. This Super Grip needs to get behind the dead bolt in order for it to work at all. Since my dead bolt is flush up against the door, the dead bolt can't slip inside the 'pocket' that's part of the strap. I called the company, they recognized the design flaw and had no fix. I returned the product. They could have at least put a disclaimer on the product description.
If they fix the design flaw, this would be an amazing product. Affordable, portable. If you have the proper dead bolt, buying this is a no-brain'er. If I had the proper dead-bolt or if this was designed differently, I would have bought one for the front door, one for the back door, and one for traveling.
I'll just go back to using my duct tape. See the attached photo.

SGL is a fantastic product, but it didn't work on 3 out of 4 doors I tried.
1st door's deadbolt was too flush against the metal plate. I couldn't slip the SGL over the lever at all. SGL needs to be thinner.
2nd door's deadbolt was too far from the doorknob. I get why they do it–the deadbolt is high enough that crooks trying to fish for the lever from under the door have to have a really long fishing gadget. But it means the SGL won't work because it's too short.
3rd door's deadbolt lever was okay, but the angle was almost vertical, so the SGL didn't work too well. It didn't have enough leverage. Also, with the lever nearly vertical, the SGL needs to be longer.
4th door worked perfectly. The lever was the old-school kind that looks like T-shaped handle, and it stuck out about 1cm from the door, so there was plenty of room for SGL to catch on and wrap around. It also locked at near-horizontal position, so the leverage was super strong. The doorknob was within reach.
1 out of 4 is better than not having any protection, I suppose. I hope they improve the product to address the other issues, especially the flush-fitting lever that is so common at hotels. At least make it longer please!

I recently spent $4,500 per door for for 4 security doors. I am confident the doors cannot be kicked down or even chopped through but…The problem is, despite what the company told me, I am concerned that any lock can be picked and all too many times even bumped. Due to my lack of trust in a potential weak point, I started looking for a security devise for the dead bolt.
I tried the other deadbolt security devices sold on Amazon and at locksmith shops. Due to my unique locking system, none worked. I was about to have a machine shop custom make 4 of them for me. Before doing so, I read the sales data and customer reviews on this devise. I decided that I could afford to risk 9 bucks. Like some other reviewers, my locks are vertical. If you read many of the 1 star reviews, their complaint is this devise does not work if the knob is locked in the vertical position. By following the directions for the horizontal knobs, they were right, it did not work. I fiddled with it a bit, reversed the direction then low and behold, it worked. Out of all the devises I purchased this simple and cheap devise worked.
I have used it for two weeks and it is secure. Since the flap is not a heavy material and since it is largely made of Velcro, it will wear out based on use where as the ones made of metal will last much longer. Still, for $9, I will just replace them when the time comes. Tonight, I am ordering 7 more: 3 for my other doors and 4 as backups. I will take one of the backups with me on my next trip in the event that I can use it on a hotel door.

I'm always looking for good security devices for hotels. I have a couple of different devices–door jams, alarms, security bar, etc.. I just bought the 2 piece lock that supposedly fits in the gap between the door and the jamb, but it would not work with the hotel door on this last trip. However, this little piece of velcro which weighs almost nothing and takes up no room in the suitcase is brilliant. We have some deadbolts at home, but the distance between the knob and lock is too great, but this worked perfectly on my hotel door. Most hotel doors have deadbolts fairly close to the knobs. I did have to play around with it at first trying to figure it out, but once I figured it out, I thought it was very secure. It would be extremely difficult to turn the deadbolt even from the inside. I don't see how it would be possible from the outside even with a key. Of course, there's always the issue of being in a fire and no one can get in; however, getting out would only take a second as the thing comes off easily just by peeling the velcro. I've had other devices that take longer, & I'm sure that the 2 piece thing would take longer.

Works so well it broke the internal mechanisms of the lock with enough pressure applied to the door handle. Hotel engineering had to come to get us out of the room, but that’s the better than the alternative. Travels well, easy to use, no issues with Velcro (yet?). 5 stars.

I can’t believe this item has bad reviews. It works so well! I’ve been at an Airbnb for over a month now while I renovate my home and I’ve been using this since. Super easy to use and gives me a peace of mind every night! I would definitely recommend.