Reddit reviews ZEN 379 Slim Cigarette Filter Tip - (1) 200pc Bag

It has a minute filtering effect... (Pull out the filter, unravel it, and examine; after finishing)

If you actually want to filter a joint, get some roll-your-own tobacco cigarette filters, like these.

EDIT: just an FYI that your lungs are self-cleansing... They naturally clean out the resin from cannabis smoke. Part of the reason tobacco cigarettes are so devastating to the lungs is because the tar from tobacco cigarettes is synthetic, and not organic, like cannabis.

Your lungs can easily clean out organic cannabis resin, VS tobacco cigarettes synthetic tar.

That's why cannabis actually slightly improves lung function and dilates the bronchi, instead of harming lung function.