I have had a Shark vacuum for several years and have never changed the filters. Finally he started playing and only the wand worked and not the main part. For this filter pack, which only costs $2-3 more than 1 regular vacuum cleaner filter, you get 4! The assembly went smoothly, it was quite fun. I thought the third filter was a bug or for a different model, but I found it on my unit and replaced it. It's like a new vacuum cleaner again! They will definitely be on my save list for future reference. I think with 4 packs and the speed at which I change them this could last a lifetime but just in case I'm following the instructions.