Bubble pack envelope is not sufficient for old matchbooks with matches. The heads are very brittle and it doesn't take much to make them crumble.

I use a small box with cotton padding inside, like the kind cheap jewelry comes in. These are small enough so you can put them inside a bubble mailer to provide a second layer of crush protection.

An alternative is the small snap-lock boxes made of a rigid, usually clear, styrene plastic. These can be purchased for 50-60 cents and do a fine job also. Again they should be put inside a bubble envelope for added protection.

My comments relate to old matches. I wouldn't go to this much trouble if shipping a few current back strike matches. They are not as brittle and their value doesn't justify the cost.