This is an Eppendorf holder with 58 usable holes (86 total).
I designed it for 1.5ml eppendorfs but if you find other uses for it then go ahead :)
The reason why it has 86 in total is that I made the holder a perfect triangular based pyramid, so which ever face you place it on you'll always have 58 holes to use.
I consider this a space efficient holder for the number you can fit on it, however I don't know whether it can't be printed on certain printers as its 13.4 cm's high and 15.1 cm's wide.
I know it can print on a Makerbot Replicator 2 plate bed. From a resolution standpoint I have no idea! There are small parts in the holes which may interfere with each other but if someone could be really helpful and tell me to help others it will be appreciated!
This is pretty big so might need quite a bit of plastic.
Please comment any problems you may have or even some improvements you might think of.
Update | Mini Version
I decided to create a smaller version of the original..well one with less holes as I'm sure a few people wont be using that many eppendorfs at once, plus it should make it more likely to print on smaller printers.
This version has 34 usable holes and 52 total.
Update | Micro Version
Just for the fun of it I made a Micro Version.
Not sure how balanced this will be with eppondorfs on it.
This version has 14 usable holes and 24 total.