I really love this floss as it glides smoothly between my tight teeth but doesn't get stuck. It also lasts pretty long. Unfortunately the floss itself is made from nylon which is a thermoplastic polymor made made from petrochemicals through a process called polymerization.
I have tried other brands that are 100% plastic free made from corn starch unfortunately they are too thick, get stuck in between my teeth, make a loud screeching noise and hurts. As oral hygiene is so important for me and that this brand is both vegan friendly and does the job really well is why I continue to use it despite the plastic.
This is what non vegan floss uses the same nylon just without harming animals. I hope in the future that this can change as plastic has a negative effect on the environment releasing microplastics that end up in human and non-human guts. Even when I dispose in general waste I have no control where it goes too and could potentially harm some life choking it.
As to the cover it doesn't last long as its cardboard so I'm reusing an old plastic dental floss plastic casing that I have. Altetnstive a pair of scissors would help. Maybe Humble co could make use of a biodegradable durable casing material.
I purchased this floss from Boots some years back and goes a long way.