Keeping chicks warm for 10 car ride

[hoosierhens101]

I have someone buying 17 chicks. They will be 10 days old on pick up day. They have a 10 hour drive to their new home. Any ideas on what I can safely put in their box to keep them warm that doesn't cost too much?

 

[neo71665]

https://www.amazon.com/HotHands-Hand-Warmers-Odorless-Activated/dp/B0007ZF4OA

They sell them at wal-mart in the sporting goods department