If you have an above ground pool with a filter unit like the one pictured, it may not fit a standard Intex Type A or C filter. That type fits loosely in the housing but does not seal on the top or bottom, allowing all kinds of debris to get past it. These adapters will allow you to use this type of filter with the pool. I have also included a replacement part for the original pump locking collar in case you are having no problem finding the original filters, but have lost or broken that part.
This part was created in Onshape, so you should be able to find it in the public files and modify it if you require.