The Lizard Skins Lock-on Logo grip is 31.06mm in diameter.
The Lizard Skins Lock-on North Shore grip is 30.94mm in diameter.
Both were measured using a digital caliper, and assuming a small difference in diameter due to texture, they are nominally 31mm diameter grips.
The thinner Lizard skins grips measure approximately 29-30mm, again depending on texture. For instance, the Peaty measured 30mm, and the Charger measured 29mm, but was difficult to get a consistent measurement from because of the type of surface.
I hope that helps.