I used these vents for having access to the "wand" on my blinds to open or close them. I didn't use them to access the window lock or to open or close the window. They work well for what I need them for, but I would recommend maybe reinforcing the hole in the actually plastic window covering with maybe packing tape or something else, just so it doesn't rip. The Velcro used to open the vent is pretty strong, and I'm afraid I'll rip the window plastic. It is really nice to be able to get some sunlight in!These things are a game changer. I use them specifically so I can continue to open my shades even in the winter. They go on fairly easy and look nice . There's also different sizes as well. Note that this is only the ventilation kit, and not the window plastic (which you will need to buy separately).I'll also say that I did have an instance where the velcro sticky parts melted and came loose on my front windows. This was because there was a lot of direct and trapped sunlight. I was able to put it right back on though and now that it's been colder haven't had any more issues.I got these hoping to use them not for the window locks but to allow me to access the window blind open/close rod. They work well for that too! The plastic film is puckering a little around them so I'll take the hairdryer to them again and see if that snugs them up.I do wish they were re-usable given the price point. Or a lower price point. They are slick but I'm unsure I'll purchase them every year for as many windows. I may have to pick and choose which windows really need them.This is the product I've been looking for! My baby's room gets quite cold in winter, but I didn't want to use the window insulation films because of ventilation issues. I hoped the curtains would help, but unfortunately it was not enough. I'm glad that I found VENTKIT. Now I can not only keep baby's room warm, but also ventilate the room as often as I want. It was very easy to install. I installed three kits on one window, which took less than 10 min. It was convenient to detach the kits for ventilation and reattached for insulation. See the attached photos of the kits. I highly recommend VENTKIT for those who want to prepare the room for winter!These make life so much easier. They last the entire season tooActually works, attached on to the film easily. I used a sharp knife to do the cut out. Provided good ventilation flow. In the picture I stuck the covers on to the edges so I didn’t lose them. Would be good if they were a little cheaper.I bought a package of Ventkit and I can tell you this is a major go!It is easy to install and use and I would highly recommend to anyone who installed the window insulator but also wanted to get some fresh air outside the window conveniently.My wife hates not being able to open the blinds in the winter, when we put plastic over most of the windows. After finding these vents, she no longer complains. Easy installation and a good seal. I will be buying more for next year.