eThe self-developed spring box of our company is made of fiber-making nylon, the physical structure is more stable,and you can adjust the width ，from 35mm to 50mm.It can effectively reduce the wear of door plate and reduce the noise。Payment Terms: 50% for deposit, 50% before shipment.(TT,Paypal ,L/C ) Package Details： Carton packaging ,one set one carton. Delivery： 25-30days after order confirmation . 1: How to confirm the quality with us before starting to produce? A: We can provide samples and you can choose one or more, and then we make the quality according to that. 2) Send us your samples, and we will make it according to your quality. 2: How to solve the quality problems after sales? A: Take photos of the problems and send to us After we comfirm the problems, within three days,we will make a satisfied solution for you. 3: What about the price? A: We promise the price we offer is lowest if same application, only to enlarge the market share. 4:What is your payment term? A:payment<=1000USD.100% in advance. Payment>=1000USD.50% T/T in advance,balance before the shipping.