A side note on using poly bagging instead of corrugated cardboard shipping containers.
[I guess feeling particularly rambly today to avoid listing items. This post arose from stumbling across the following in the UPS Service guide today while looking for Dim Weight info details]
– Items Shipped in Bags: Shape – When multiple items are shipped in a flexible container (e.g., burlap or plastic bag), the package measurements will be determined when the exterior is at rest. As this shape will differ from placement to placement, cubic size or package measurements will be made at the sole discretion of UPS. Tails – A tail on an item shipped in a bag should be measured for the amount of space it takes up in a reasonably compressed fashion. Any tail that is created by placing an item in a bag must be compressed and taped to the body of the item.
FedEx doesn't go into that explanatory detail in their service guide, but it is assumed and implied by general statements in the FedEx tariffs.
It can have some bearing on shipping backpacks and other large items that are less subject to breakage or damage, and can be an option in some cases to reduce weight, and the hassle of having to construct a custom box to avoid dimensional weight and crossing size thresholds.
USPS doesn't care about poly mailers one way or the other as long as they are firm/tight (in the sense of not having lots of saggy material that can get caught in machinery. Like a 1 ft square object tossed into a 2 ft square poly bag). I believe you can actually just slap a label right on a suitcase or backpack (making sure it can't come off) and mail it.
UPS and FedEx are a bit stricter. I have shipped suitcase like popup show displays (right in their zipper nylon cases) and suitcases using FedEx with no problem. Note that these are items meant to be used, not items sold to buyers, and are expected to pick up scuffs, dings, and dirt same as if taken on an airplane as baggage. FedEx has special label pouches that ziptie right around the handles and it's fine. (Does incur a $12 additional handling surcharge due to not being in a box and in the case of the display, being very long. Still cheaper than an extra bag on airplane) UPS is about the same on this issue.
Anyway, another consideration that I've pondered for a while is dimensional weight of poly bagged items. Depending on the contents, they can deform, the dimensions change, and actually end up bigger for purposes of dimensional weight (I posted a poor demonstration of dimensional changes for a cardboard box that gets stepped on somewhere here a while back)
Although the actual volume of a deformed package doesn't change, the volume of the containing rectangular box calculated using the max dimensions of the deformed box does. This directly affects dimensional weight calculations, can happen in transit, FedEx measures new large, smashed size, and post bills for the difference.
Shipping Volume = 300in²
Stepped on it and it becomes Shipping Volume=432in²
example: for the above pkg as an eBay FedEx Ground shipment that uses a 166 divisor,
the dimensional weight of the original package is 10x10x3/166 = 1.81 = 2lb
the dimensional weight of the smashed package is 12x12x3/166 = 2.60 = 3lb
Not much, but a surprise when the additional charge arrives.
The same is a consideration for poly bagged pkgs, depending what's in them. A backpack, fairly tightly bagged probably wont change shape much. Some other items could "flow" in the bag, especially if loosely bagged (clothing, multiple plush toy, etc) and the apparent volume of the bag increase same as the box did when stepped on.
As far as shipping backpacks in poly bags? If new and pricy, maybe not. If used - backpacks are meant to be used hard anyway in the great outdoors and can take some punishment - then maybe.
A lot of the same things that could mangle a backpack frame in transit are going to do it whether in a box or a bag. Dents, and scuffs more so in a poly. Wrapping any exposed frame metal in bubblewrap, or folding a piece of cardboard over could alleviate dings and scuffs issues. Or a faux box inside a poly could make packing easier than fabricating a box (2 big pieces of cardboard with backpack sandwiched in between, and even some sides folded over if getting fancy.)
Keep in mind that FedEx and UPS might add additional handling surcharges for a poly bagged pkg like that (there is no provision for it in the eBay FedEx label flow, so if they caught it it would come as an added charge when invoiced later. UPS I don't know how it would be handled or if it can be specified at label time)
I included the Priority Mail stuff just to recap what you said which was 100% correct, and included the international stuff for general info and completeness since I was laying it all out for FedEx and UPS.
Have no idea why you are mentioning Price Groups. I said nothing about them - only that Dim Weight isn't a factor in USPS international shipments at all. (And length + girth limits are a country dependent factor for international)
I simply added to what you correctly posted.
The rest because you didn't recall correctly, and used the wrong FedEx Dimensional Weight Divisor and computed the wrong FedEx Dimensional weight in the context of eBay shipping. That can confuse everyone, including the people that google it a month or a year from now.
Didn't mean to step on your toes
Have no idea why you are mentioning Price Groups. I said nothing about them - only that Dim Weight isn't a factor in USPS international shipments at all. (And length + girth limits are a country dependent factor for international)
I simply added to what you correctly posted.
The rest because you didn't recall correctly, and used the wrong FedEx Dimensional Weight Divisor and computed the wrong FedEx Dimensional weight in the context of eBay shipping. That can confuse everyone, including the people that google it a month or a year from now.
Didn't mean to step on your toes
If we can bear it, I'd like to reiterate one point that has been mentioned but might have been lost in the shuffle: For packages up to 84 inches, Parcel Select and Priority Mail will cost the same for buyers in USPS Zones 1 - 4; it's only the farther Zones that incur the dreaded dimensional weight. So it makes sense to offer Priority, too, or use it as a surprise upgrade for the closer buyers.
