Installation

You may list collective.behavior.size to buildout.cfg or setup.py in your own package.

zc.buildout and the plone.recipe.zope2instance

Use zc.buildout and the plone.recipe.zope2instance recipe by adding collective.behavior.size to the list of egg:

[buildout]
...
eggs =
    ...
    collective.behavior.size

Dependency to your own package

You may also list to install_requires to setup.py within your package.