Usually, there are 3. 3 extruders 3 layers. More layers usually mean better quality of the film. The trend for this application (shrink film) is moving to 5 layers (5 extruders). Also due to the circular economy, you need to put recycled content in plastic packaging which goes in the middle layer.

@@gonjonjokos ohh i get it now thanks for making time to reply me :) also, i want to ask one more question.. then, is this an example of co-extrusion? sorry if I'm askimg too much. I'm not an engineering student but i take a polymer class so i have to learn about it :')

@@rsa3264 Yes this is coextrusion. Mono blown film extrusion lines in Europe are now only used for films for bags, construction films, and other simple applications.

@@gonjonjokos ohh i see! thank you so much for your explanation. it helps me a lot ☺