You can use any labels on our compostable poly mailers, but we would recommend buying one of our sample packs first to double-check the performance of your particular labels on them. We do extensive QA testing with our mailing satchels and our own labels and are able to guarantee that they work together, but we are unable to test all label brands in the market.
We would also strongly recommend using compostable labels on compostable mailers, otherwise the label will have to be removed from the mailer before composting and that's often very tricky.