USPS Standard First-Class Letter -Is there a rule about Unbendable ietms?

[dreambooks]

I went to the Post office today to ship something thin and light using an envelop. I usually buy postage online from Ebay, like the first-class package, which costs $5 in this case. So it gets me thinking, why don't I mail it in the standard letter and save a few bucks because the item is not sold too much. Plus I heard that people shipping CDs without jewel case using standard letter, and I had received small items from people just using standard letter. To my chagrin, I was told that I need to ship it package because it is unbendable! My item is not totally rigid as it is like a tablet of several small items. Is there such a rule? I know my letter is less that 1/4 inch, and meets the required size limit, and weighs less that 2 oz. I really want to save a few bucks for this small item.

[dreambooks]

By the way, it is a tablet of small button batteries.

[buyselljack2016]

Possibly could have been sent paying the "non-machinable" surcharge. 

That of course provides no proof of delivery. 

ETA:  can the batteries even be "mailed" via a 1st Class envelope?

[ebooksdiva · Accepted solution]

FYI Lithium batteries need to be shipped ground. They are definitely not machinable. So you should ship it in a package. And for your seller protection with tracking. 

[1786davycrockett]

If you're talking about the eBay Standard Envelope (ESE), you're out of luck -- for a couple reasons.

First of all, you can not use the ESE for  "a tablet of small button batteries."  The ESE is limited to postcards, stamps, trading cards, paper currency & coins.  Obviously, batteries are not included.

Secondly, the ESE is treated as "metered mail" by USPS, which means that it routinely must travel at high speed through a long series of machine rollers, which will bend the envelope into numerous curves (these can be viewed on various USPS videos on-line).  Any item which is unable to withstand these machine rollers will be considered as non-machinable by USPS, resulting in additional postage being necessary, either by the seller, or by the buyer.  

And buyers do not react favorably to receiving mail marked "Insufficient Postage."

[nobody*s_perfect]

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@dreambooks wrote:... I heard that people shipping CDs without jewel case using standard letter, and I had received small items from people just using standard letter. To my chagrin, I was told that I need to ship it package because it is unbendable! My item is not totally rigid as it is like a tablet of several small items. Is there such a rule? I know my letter is less that 1/4 inch, and meets the required size limit, and weighs less that 2 oz.....

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To address the original question: Rigid pieces CAN be mailed as letters, if you pay the "nonmachinable surcharge" which currently is 40 cents.  You can see detailed "nonmachinable" criteria in this section of the DMM:

https://pe.usps.com/text/dmm300/101.htm#ep1046732