an eye for an eye

an eye for an eye and a tooth for a tooth

eye and eye turnbuckle

eye relief (=eye-point distance)

eye relief，eye distance

eye to eye contact

eyetoeye contact

anti-ballooning apparatus

anti-ballooning ring

anti-ballooning wire

Apical ballooning

ballooning

ballooning degeneration

ballooning effect

ballooning instability

Ballooning mechanism

ballooning mode

Ballooning modes

Ballooning theory