For 3.5", yes. 5.25" disks could be removed from their protective enclosures, inserted into a drive, and used as normal. At least until the exposed medium was damaged by fingerprints or other debris. Not something you would normally do though. Source: Did it myself a few times mostly out of curiosity.
This. When my favourite floppies started to have a worn sleeve (especially 3.5", where that metal protective covers started to bend out a bit, threatening to jam in the drive), I usually transplanted the disk itself over to a new sleeve.
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For 3.5", yes. 5.25" disks could be removed from their protective enclosures, inserted into a drive, and used as normal. At least until the exposed medium was damaged by fingerprints or other debris. Not something you would normally do though. Source: Did it myself a few times mostly out of curiosity.
This. When my favourite floppies started to have a worn sleeve (especially 3.5", where that metal protective covers started to bend out a bit, threatening to jam in the drive), I usually transplanted the disk itself over to a new sleeve.