The Gsport site
Looking again, it seems as if they list the pleg 2+ core and sleeve, and single sleeves, but that they aren't compatible with the pleg2 cores
You might need to upgrade your core to then have access to single sleeves in the future
Looking at the 1.5" diameter spec, they might have done this to make it fit more forks, as most don't fit pegs bigger than 1.5" as the old plegs were