The HDPE Containers are durable round bottles that store easily and save space.
Nalgene says:
Nalgene HDPE Containers - 2 Pack
Round bottles that store easily and save space. Made of durable white HDPE. Dishwasher safe (top rack). With independent screw-top caps.
Wide mouth means its easier to spoon your instant coffee in without making a mess. Used for many years, very reliable. The tops are particularly grippy making these jars easy to open and close.