How To Use Progressive Web App aka PWA On 420 Magazine Forum
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They are duct tabs. They are optional to use. They push onto the collar and flare out a little so the wire coil in the duct slides under and secures more effectively. Makes it easier to duct tape! They can also be used individually as a spacer if fitting a fan directly to the filter, and its smaller than the collar size.
If attaching ducting to the collar of your filter, slip these down onto the rim with the tab facing out and down. These will assist in installation of ducting. Slip ducting over tabs, they will hold it for for you while you apply tape.