Guangzhou Casen Door CO.,LTD strictly selects the raw materials of half glass interior door-soundproof door. We constantly check and screen all incoming raw materials by implementing an Incoming Quality Control - IQC. We take varies measurements to check against collected data. Once failed, we will send the defective or substandard raw materials back to suppliers.. We receive important feedback on how our existing customers' experience Casen brand by conducting customer surveys through regular evaluation. The survey aims to give us information on how customers value the performance of our brand. The survey is distributed biannually, and the result is compared with earlier results to identify positive or negative trends of the brand.. At Casen wooden door, we offer expertise combined with personalized, one-on-one technical support. Our responsive engineers are readily accessible for all of our customers, large and small. We also provide a wide array of complimentary technical services for our customers, such as product testing or installation..