Strong Grey Opaque Polythene Mailing Envelopes. Our Alphasacks have a permanent easy peel and seal lip and are 100% opaque. Our bags are made using a 60mu 100% recycled polythene and they are strong enough to deliver most goods safely. Prices are negotiable on larger quantities and we can print our bags up to 6 colours, minimum quantities will apply for ths service. The address labels on the bags pictured are not supplied, we can manufacture self adhesive printed address labels to any size and style you require, please contact us for further details.