Not recommended/don't do it--- why do you want to do this?
Hatcheries ship 25 or more together so they can keep each other warm, and they ship 1 day old chicks- as they can survive 2-3 days on the remaining yolk in their abdomens. This is still hard on them, and shipping losses often happen. They pack them in to a small but strong box with air holes and a pad for traction and a bit of insulation. Older birds can be shipped- like 3mo and up, they are old and large enough to keep themselves warm, and will eat apple slices packed with them to keep from dehydrating and dying. A week old chicks is a fragile thing, they need to stay warm and have access to chick food & water at all times. The boxes can get turned upside down, there is no way to send food and water with them, even if you got a battery pack heater to keep them warm. You need to wait until they are much older and can survive 2-3 days on apples or similar. If a person wants these, they need to pick up or you need to drop them off in person- or wait until they are much older to ship.
pack them with a couple of hot hands. those are in the sporting goods store. they activate with the air and stay nice and warm for 18 hours. most of the off brand names will only last 8 to 10 hours but the brand name "hot hands" will last 18 hours. the chicks will huddle on them to keep warm during shipment. That will at least give them a good chance at shipping. also put lots of pine shavings in the box for them to huddle down in. that will help hold the heat in also.
oops i thought these were day old chicks. you cannot ship 1 week old chicks. they will die.
I agree with this if you really need to ship four chicks. Seen those things all over and not only HOT HANDS, you can also find some heaters in pet stores where they get their fish mailed by UPS or USPS. It is very simliar or same as Hot Hands. Also some apples. For THAT young, can you wait awhile so they will get a bit older like amonth old up to three months of age?
Ive had 15 chicks shipped in the dead cold in Feb by Ideal to me and no losses.