This is a review of the K&F Concept clip-on 67mm Circular Polariser Lens filter Clip for Mobile Phones.I've bought several bits of K&F kit and have found their products to be very good.In fact I bought one of their UV filters to try out two years ago this month and was that impressed with it that, when upgrading some of my Dslr lenses, I switched all my UV filters to K&F's.They are excellent quality, well made and at very reasonable prices compared to some other brands.So when I saw this clip-on type for phones, whilst already having one for my Camera and not having thought about one for the phone, I thought I'd try it out.It says it's for iphones on the listing but, trust me, I'm using Android…your lens can't tell what phone it's in and neither can the sunlight so it will work with any brand of phone.If you've never used a Polariser on a camera before it will help if you do an online search and look up what they do and when to use them.I presume the couple of negative comments are due to not understanding how they work as, over the last 45 years of using Dslr's, the only changes to Polarising filters have been when we switched to digital and they changed from Linear to Circular due to how digital cameras work.I've experience with both types…this one 'does' work.It's basically like putting sunglasses over the lens to cut down on glare, enhance the colours and give you improved clarity and contrast.Their main use being to give you deeper blue skies and cut down on reflections from water…rivers, ponds etc.The 1st pic I've added is the before shot with the 2nd pic showing how it's deepened the blue of the sky.This item consists of a 67mm Polarising filter that screws onto a plastic clip and just clips over the top of the phone, it has a decent strength spring so it's unlikely to fall off yet is still easy to put it on and remove it and it's supplied in a little eva hard case.It's a slimline filter too so at 67mm you won't see it in any of the pics you take, even on wide-angle shots.And being a standard 67mm filter you can take it off the clip and use it on your Cameras too.Once you've got it over your lens you rotate the filter, carefully, until you see the image go a bit darker then you take the pic.You will see your screen going darker then back to lighter then darker again as you rotate the filter and this is how you know it's working.Polarising filters work best with the sunlight coming in at a 90 degree angle to the camera so if you're facing directly to, or away from, the sun you'll not notice much effect.They also reduce the light getting to the lens so if in manual mode you need to compensate for this and open up the exposure by one or two stop.Or leave it on auto and let the phone do it for you.Considering the price at c.£17 it's a bargain, the filter alone costs £11 and you can unscrew the Polariser and use other filters if you wish to so it really is a handy little bit of kit.Another K&F Concept winner.