Custom molding specially in automobiles, defence, aerospace requires that the manufacturer works with the customer closely and gets its product approved - tailormade to customer needs. This takes 2-4 years and requires working jointly with the customer. This in itself is a moat since its difficult for the customer to find an alternative supplier whose product can exactly match his requirement, Hence this is niche and has higher margins and customer stickiness. Adding new customers is not easy and takes time but recently, sintex has added some new automobile manufacturers.Their European Subsidiary is well known for custom molding and management plans to bring superior technology from european subsidiary to Indian parent.
Sintex retail products can be compared to other plastic moulders but sintex brand has 70% market share and with GST this seems to only increase (unorganised to organised play).
I suggest go through their audio concalls for last 2-3 years, presentations, research reports, annual report and connect the dots. The Management are not good in clearly communicating their thought process and hence the investor community is left guessing their intentions.