If you have a bagged vacuum, you’ll find a lot of third-party dust bags being sold online that are marketed for your vacuum. Though most of the time they will fit your vacuum, I recommend that you should opt for original bags whenever possible. However, sometimes, the original manufacturer would phase a type of vacuum or a kind of dust bag out of the production line. As an example, many Electrolux canister vacuums and dust bags have now been phased out of production.  In this case, it’s perfectly okay to get third-party vacuums to extract a few more years out of your vacuum. But beware that third-party bags tend to have worse quality than original bags. It’s just safer to just buy from the same brand that sold you the vacuum if you still can.