rubygems

∴ rvm rubygems [version]

Installs a specific rubygems version in the current ruby. If
'current' is specified, the most current rubygems known to RVM
will be installed.

Currently compatible with only MRI 1.8.*, 1.9.* and Ruby 
Enterprise Edition. If your system is not supported, running the
command will generate an error message.

MRI 1.9.* ships with a version of RubyGems. To revert to that version
after installing a custom version via 'rvm rubygems' run 
'rvm rubygems remove'.