With the market development tendency of the co-extruded blow film machinery, SUN LUNG can offer various kinds of gearbox type to fit with blow film machinery requirement, such as A-B-A or A-B-C co-extruded blow film machinery, or just one-layer blow film machinery. The A-B-A blown film machine consists of two extruders, normally of two different sizes. The most common ones today are the combination of a 45mm screw diameter together with a 55mm for T-shirt bag production. In the A-A outer layer, normally 20% of CaCO3 is used, with some additional of color master batch, LLDPE and a larger percentage of HDPE. The B layer can be used with larger percentage of CaCO3 with HDPE raw material. Generally, SUN LUNG offer SL-20~SL-100 gearbox type to these popular blow film machinery.