I used to be a whole grain advocate and used a special microwaveable Thermos bottle. It broke due to constant use and no replacements available. Put in grain, water, flavoring and microwave till water boiling. Quickly put cap on and 2 few hours later they were done. Looked for years and nothing on market. Saw this one on eBay and it worked great. Bought another to have when current one dies from usage.
Thermos is light weight, but sturdy. Seals tightly and holds a good amount. Meets the need I have to take hot items in my lunch and keeps it warm enough that I don't have to use the microwave.