Coattails customer-examples of listed companies with dependence on one customer

Customer concentration is good and bad. Good because it indicates there are some loyal users of your product, bad because they have pricing power. Some examples below:

1. Nile Limited (manufacturer of lead acid batteries) supplies 80% of its output to Amara Raja(another unrelated listed player). This exposes it to risks of revenue loss
2. Vakrangee (a last mile B2C/B2G/G2B kiosk) has run up due to its tieup with the global 800 pound ecommerce gorilla Amazon, where the tieup allows Amazon orders to be placed via(and delivered to) the Vakaranjee Kendra. Not yet key person risk, but still significant. 
3. Future Consumer products(FMCG asset light play of Kishore Biyani) gets ~70% of its revenues via the Future Retail and other related(not owned by it but by promoters) entities. This makes it akin to contract manufacturer
4. Solar Explosives gets ~30% of its revenues from Coal India. Of course, to put this in perspective, 90% of the explosives use in India is industrial, and coal mining is a great chank. So this is understandable. 
5. Manpasand Beverages(listed beverages player) gets 25% of its revenue from Indian Railways via the mango/apple flavour drinks sold on the trains/railway stations
6. This list excludes franchises/exclusive players which have different risks such as 
1. Page India(For Jockey)
2. Jubilant Foods(for Dominas)
3. Westlife(for McD)
4. Varun Beverages(for Pepsi)

In all these companies, there is always a disruption risk apparent and/or risk of dispute etc. Hence, one should take care while seeing the financials-whether this is a contract manufacturer or branded player in reality-one indicator is margin volatility etc. Also, IND-AS has some guidance on take or pay contracts, so thats useful too