MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
If you need them to be stronger then you can use the solid aluminum ones here: http://openbuildspartstore.com/black-angle-corner-connector/
The main difference is the on these they have the hole size of 7.2 that allow for using them with the M5 screws or the OpenBuilds eccentric cams:http://openbuildspartstore.com/eccentric-spacer/
This way you can add adjustable wheels to your project.