What sizes do the white spacers come in? I know there are 3-4. What are the pros and cons of theses spacers compared to the black ones? Besides online where can I purchase either spacers? (Home depot, lowes, etc.)
Here is the VEX Product Page for Spacers: http://vexrobotics.com/spacers.html
As you can see under “sizes”:
Nylon spacers
Diameter: 0.500"
Hole: 0.194"
Height: 0.125", 0.250", 0.375", and 0.500"
The advantage I find with them is simply their different sizes. The smallest size we normally use to separate two pieces of metal when we create a joint with a long screw & nylon lock nut. Also, the larger ones make creating large amounts of spacing easy, when you don’t want all the weight of two extra collars.
The last thing would probably be just that they have a larger surface area, keeping the two pieces of metal on a joint from bending at the joint as much.
As for purchasing them anywhere but online, I unfortunately would not know, as I have not seen or looked for them anywhere. Maybe someone else can help out.
~Jordan
white has more choices
black fits in places that white doesnt
You can also buy the spacers from here. I like the white spacers personally, You just have to get the right size that meets the spec of the VEX spacers.
I also machine my spacers to fit in places they normally wouldn’t one of the advantages of a lathe in my garage I guess.
Anyway thats what I do.
- Andrew
Edit: on that page you want to click on Nylong 6/6 spacers Female unthreaded spacers.
White spacers do not fit on the edge hole when there is a 90 degree angle next to the hole. Other than that, white spacers are extremely versatile.
White spacers are sized in exact fractions of inches, so if you want a spacer that is exactly the same as the distance between holes in vex metal, or the length of the shortest standoff, then white ones are better. This also matches with shaft collars, delrin bearings and other standard components.
The larger diameter also means chain runs over them pretty smoothly to make chain tensioners.
Black spacers are sized metrically, so you would need to use some spacers plus washers in the same situation. The main advantage of black ones is their smaller overall diameter for fitting up against flanges as SweetMochi said.
We have found that white spacers are easier to fit screws into, and they spin easily on screws, whereas black ones can offer some resistance. I think the black ones were only designed for shafts, so if you have a pivoting joint using a screw, use the white spacers.
Pros for the white spacers:
-The sizes are in fractions of an inch, extremely useful.
-As Jordan said, the larger surface area means that whatever is next to them won’t wiggle/bend so much.
-They are incredibly versatile.
My favourite bit about them is their versatility, I have had troubles with the black spacers, like them squashing (so they then aren’t the size they would normally be next time you use them), and in one or two cases they have cracked and broken when overtightened. I know I shouldn’t have overtightened them, but hey, we all make mistakes. My point is they aren’t very forgiving in those circumstances.
On a side note, I found that the conversions for the black spacers in inch → cm is incorrect on the product page. It says on the product page:
Thin Height:0.190" (4.6mm)
Thick Height:0.330" (8mm)
Yet when multiplying 0.19" by 2.54 (to convert it), I get 0.4826 cm or 4.826 mm. Similarly for the thick spacers, 0.33" x 2.54 should be 0.8382 cm or 8.382 mm.
Is it just me that gets different numbers? 
And do you then go with the millimeter measurement or the inch measurement?
~George
Looking at the CAD models, I get different numbers. I’m assuming that the CAD models are correct, but for the “thin” black spacer, I get 0.187 in or 4.75 mm. Then for the “thick” black spacer, I get 0.328 in or 8.331 mm. It looks as if the inch measurements have been simply rounded, but for some reason have another 0 added on the end, and then somehow their conversion factor from inches to millimeters was off.
Great find, by the way, and thank you for pointing this out!
~Jordan
Using the admittedly primitive method of empirical observation, I grabbed some spacers and measured them. The larger black spacers are 8mm long, and the short ones are 4-and-a-half mm (I’d buy 4.6, but my eyes aren’t quite good enough to tell the difference between 4.5 and 4.6 mm on this ruler). I admire the enthusiasm of anyone who measures the length of a VEX component to the hundredth of a millimeter! This could lead to a lengthy discussion of the difference between accuracy and precision, but I imagine that you all understand that already.
Oh, wow. I can say I was not at all expecting even more different numbers.
Thank you for measuring them! 
I would have done it myself, but the most accurate measuring device we have at my home is a simple ruler. And most of our black spacers have been squashed anyway, so my results wouldn’t be at all accurate.
I didn’t actually measure them in CAD or in real or anywhere, I was just going off their numbers. But measuring to the nearest hundredth of a millimeter sure sounds like fun 
I don’t think I have that much patience or focus myself.
Oh, and don’t ask how I stumbled upon this mistake, I don’t at all remember.
~George