I have had the Dyson DC59 cordless vacuum for about 4 years now and have never had a problem with it. It recently started pulsing when I turned on MAX mode and then started doing so even when I wasn't in MAX mode. As the vacuum is over 4 years old my next thought is that it could be a battery issue. So I bought a new battery and installed it and still had the same problem. After some research on the internet I found that this vacuum pulses when there is a blockage to protect the motor from overheating. Even though I regularly take the vacuum apart to clean it, I did it again just to make sure there wasn't a clog somewhere that I didn't see. After further research I found that another possible cause could be a dirty pre-filter. I have tested this filter and it never looks dirty from the outside, but it never occurred to me that dirt could collect inside the filter. So I removed the cap from the filter, poured water into it, shook it with water and squeezed it out. Of course, the inside of the filter was full of dirt. Since the filter needs at least 24 hours to dry, I decided to buy more filters so I can use one while the other dries. From everything that is on Revain I decided to buy these filters although they have not been reviewed yet. The price is good for 3 filters and they looked the most similar to my original filter. Some of the other filters I looked at didn't have the top pressure as the original. After getting and trying these filters I couldn't be happier. They look just like the original and are perfect for the vacuum cleaner. It was a bonus that they are also more reasonably priced than others I have reviewed. If you are looking for this type of filter, I don't think you can go wrong with this one. I hope this review was helpful to you. I will update the review if my opinion changes.