There are a lot of questions here! 16GB would hold a huge number of designs, but you couldn't just store designs on it and then put it into an embroidery machine. The stick needs to be formatted for the machine. With mine it means I would put the new stick in the machine and let it format it before I added any designs.
I don't store designs on my stick. They are all on my PC (with backups of course!) I use a 2GB stick to put what I want to use on and then take it to the machine. The more designs that are on it, the longer the machine takes to read the stick. When it gets too long for my patience, I delete all the designs and start again.

I use an usb stick just for backup of my designs. I have a usb cable to connect the laptop to the brother machine. Then on the pc it opens as onother drive and so I put the design on this , and the machine understands what to sew.

My Ruby came with a USB-stick complete with bonus designs. I also have an 8 Gb that works well on the machine but I had to have the machine format it and I use a lot of small subfiles; that makes reading faster.
The other machine, a Melco EP-4 (which uses dst or jef) came with an USB port, but no flash drive. So a new one had to be formatted by that machine and I did the same there: many small subfiles.

And I have a 16 Gb one with my own designs as extra back-up for my design files only, not the embroidery files. I have an external hard disk and CDs too for designs by others..

Hi Toogie...lots of answers...but I use 16 GB sticks to store my designs on and I use a 2 GB stick in my embroidery machine...BabyLock and Brother do not require that you "format" the stick before hand and they can "see" designs that are not in folders as well as designs that are in folders and subfolders...but some other brands like Janome do require that you format the stick first...When I want to embroider a design...I put the 16 GB stick into my computer USB and the 2 GB stick into my computer USB and transfer the design from the 16 GB to the 2 GB stick to embroider the design. I would not just depend upon the USB sticks...still have back up files someplace else...either CD/DVD, external hard drive...etc...

I have a copy of all my designs on a externe harddrive. For the work with the machine I use an USB stick with only 1GB. I agree with Sue, a stick with more GB would need to much time to read in the machine.

USB sticks can fai just as the discs can and also the external hard drives so for me i would use several smaller usb sticks and label them as to contents with a key fob attatched to them. that way you do not have all eggs in one basket and you can see from the keyfob what is on the USB without haveing to put it into a computer first. the clear key fobs are great for this use and not too expencive to buy from Ebay.

I use 2 USB sticks to take designs from my computer to my machines and I never have more than 20 designs on one at a time. I don't like waiting for the designs to come up. I do not use them to connect to the internet. I have several USB sticks that I use to back up my designs. Each one has no more than 3 digitizers on the stick, all organized so I can put designs back into my software if and when I need to. I made a holder for my USB sticks. Each stick has its own pocket which is identified with the names of the websites. Cute and its sister sites are all on one because it is special. My USB sticks are 1 of 3 backups so I can sleep at night. Check out the Babylock Elissimos. Thanks to the new Destiny, people are trading in their Elissimos so the shops have lots of them. A great deal and a great machine. I hope you get answers to all of your questions.

Toogie I think that many others have given you great advice but for my two pennorth I have found that my machine hates too many designs on s flash drive and its easier to just have a few on it. I also have a assortment of flash drives with loads of designs on. Which reminds me its a while since I looked at many of them. I suffer from too many designs and not enough sewing time

Someone has already said 2/4 GB sticks are getting rarer ,I have had a few fail ,always format in my computer before using,The new pe-design 10 uses USB stick and worries me that it might fail, expensive to replace..

Toogie, I have an older style Brother embroidery machine and it will take any size USB that I have put in it - BUT - I only put a few designs on the stick at a time as it becomes slower as the number increases. (I have tried up to 16 GB)
I use one USB stick for transferring designs which is totally separate to any storage or back-up USB sticks.
That is all that stick is used for nothing else. So I can delete designs from it at any time without worrying about if it is the only place I have that design.
Depending on the software in the embroidery machine what file formats it will read. I haven't bothered trying any other embroidery format because I only have a Brother, so I stick to pes. (What a shocking pun!)
I did put my accounts USB (black stick) into a machine once (didn't have my "red USB transfer stick" on me that day and we were testing something on the machine's capabilities) and it could only read the couple of pes files - the machine couldn't see my accounts files or look into any folders that were on the USB.
That reminds me. When I first started transferring files from computer to machine, I put my files into folders as I do on the computer and it couldn't read the files. My paperwork for my machine says that I can store some phenomenal number of designs on the USB and the machine will read them. Did try that, but it is a drag trying to find 'THE' file that you want to stitch out. That is why I now check on the computer what is on the stick so I only have a half dozen designs at any one time on my 'transfer USB'.
I want to spend my time stitching, not pressing the forward button for ever and a day!!

I think I'm saying what everyone else is...store on a large drive but transfer to a smaller - 2-4 GB - to actually put into the machine. One other hint - I have a thing that stays in the USB port of my machine so I only put the flash drive into the other end of it, instead of my machine. Just to safe guard my machine. Doggone if I can remember what that thing's called!! Maybe rescuer will see this & know! :-)

I send my designs to my machine via my laptop using my software with a cable connection. After I HAVE STITCHED THEM I SAVE THE STITCHED DESIGNS a usb stick plugged into my machine. I label these sticks as machine back ups. If I want to stitch a second stitchout of a design , I can plug the stick in and locate it . I store my downloaded designs from all my sites to a external hard drive. If you want to store yours on a USB stick just label your sticks in categories and you can have multiple ones. Don't worry about getting them all on one stick. Kay

Wait! Wait! My 2002 computer read USB 1.0's. My newer laptop from about 2010 or 2011 reads USB 2.0's and they are about to come out with USB 3.0's, which I' guessing will not be readable in a 2.0 USB port. My son says at his retail store they are not ordering any more of the 2.0 USB's, so I think this is forthcoming! It will depend on which USB your computer AND your embroidery machine will read, when you get to that point, and lots of the newer emb machines are getting away from the USB's and giving you a cord to connect directly from emb machine to the computer USB slot.

Also, an aside, my old technology Janome 350E was supposed to be limited to a 2GB USB, but I now use 8GB sticks in it, because that is what I can buy. Up around 100 files, the machine memory or reading ability gets overwhelmed, so I don't use much of the 8GB of space. Some other machine brands will allow you to set up subdirectory folders, etc. and use bigger USB storage. Just depends on your brand. Also, some brands are very ticky about which brands of USB sticks they will read. What a mess.

One final caution, and I have read this here many times. USB sticks sometimes suddenly FAIL, so not a reliable single storage place for your files!

Hi Toogie, I have two USB sticks for my embroidery machine. One 2GB and the other 4GB. I download from my computer only the designs that I am going to use in the next day or so. When finished I delete them from the stick as I have found that when there are several designs it slows everything down.