- Sleeping bags are designed to keep people warm
- Insulated material can be used for keeping warm
- So, sleeping bags usually are made of insulated materials

- Sleeping bags usually are made of insulated materials
- Down feathers are a thermal insulator
- Therefore, down feathers can be used to make sleeping bags

So, down feathers can be used to make sleeping bags
[Question]Down feathers are used by many sleeping bag manufacturers because down feathers are
[Context]- Sleeping bags are designed to keep people warm 
- Down feathers are a thermal insulator 
- Insulated material can be used for keeping warm