Air Stone

Air Stone (エアストーン) is an enemy from Mega Man 11. It's a small security robot that uses advanced optical technology to stay invisible most of the time. However, if Mega Man gets too close, the Air Stone will reveal itself and, if not destroyed quickly enough, shoot out eight small stones and then turn invisible again. It appears in Block Man's stage.

Air Fire
Air Fire (エアファイア) is a variant of Air Stone seen in Torch Man's stage. It is exactly the same as the Air Stone, except it shoots out fireballs instead of stones.

Air Nut
Air Nut (エアナット) is another variant of Air Stone, created by Dr. Wily specifically to protect his Gear Fortress. This one appears in the first Gear Fortress stage and shoots metal nuts instead of stones.

Mega Man 11 Gallery
Air Stone

Using hi-tech optical camouflage to lie in wait until an intruder approaches, this bot shows up out of nowhere and launches showers of rock-hard bullets!

Air Fire

The fiery version of the Air Stone, this security bot blends in well in fiery areas, but tends to be easy to spot in cooler locales.

Air Nut

A modified Air Stone intended to defend the Gear Fortress. The sheer number of them is a testament to Wily's obsession with victory at all costs.

Trivia

 * Air Stone was named "Bomb de Ring" (ボム・ド・リング) during development.
 * Concept art shows that an ice variant was planned for Mega Man 11.  This variant would probably have appeared in Tundra Man's stage.