Kenmore New Style "C" Vacuum Bags 20-54321 are the same bag as the 20-50557 and 20-50558 Style C bags.
When choosing a vacuum bag for your Kenmore/Sears the best advice we can give is to look at the current bag you are using.
Most new vacuum bags are the synthetic cloth which is still a paper product but feels like cloth. It is made in such a way that you get great filtration and yet it does not loose suction and is still disposable. This is the best choice for asthma and allergy sufferers. Synthetic filter media will not support growth of mold, bacteria or mildew - fine dust retention & increased capacity without losing suction. They do not have the fold in them as the regular paper bags do so they look bigger and this makes some think they have the wrong bag or it will not fit. You just loosely fold the sides into the bag compartment and as the bag fills it will expand. If you are currently using a "synthetic cloth bag" you will see a difference in performance if you go down a level.
We do offer high filtration paper bags, such as the Envirocare 99.7% filtration or the Micro-Lined versions. They are still a great bag when it comes to filtration and quality but at a fraction of the cost.
If you are currently using a standard paper bag like the 20-5055 you can upgrade to a higher filtration bag, Style C or Q.
The 5055 (20-5055) , 50557 (20-50557), 50558 (20-50558) , 54321 (20-54321), and Style C and Q are all the same bag in regards to size and fitting your vacuum. The only difference is filtration. If your vacuum originally came with the Style "Q" it is the higher filtration, synthetic cloth bags. If it came with Style "C" it's the high filtration regular paper bag.
We also recommend changing your bag when it is 3/4 full. If you go beyond this there will be a decrease in suction and the chance of overfilling and possible bursting of the vacuum bag. And that would be nasty. So maybe look at buying a case of bags so you have plenty on hand. We also might note we find most bad smells coming from vacuums are due to a full bag or not changing the filters. Most bagged vacuums have at least one filter. We find many people don't even know they are there. Take a closer look at your vacuum or manual and you will be sure to find a compartment with a filter. If your not sure or need help locating it we would be happy to help. Just email or call us with the model number of your vacuum. (116.?????)