What is it?

Lifetime Replacement 

Lifetime Replacement provides repair or replacement services for your 2nu performance sunglasses, including unlimited incidents of accidental damage protection

Coverage: Lifetime Replacement for 2nu performance sunglasses includes unlimited incidents of accidental damage protection. Each incident is subject to the replacement fees (shipping included) below

Replacement Fee (all 2nu Sunglasses except Prescription Sunglasses): 
Australia: AU$60
Hong Kong: HK$300
New Zealand: NZ$65
Singapore: SG$55
Rest of the World: US$60
Replacement Fee for Prescription Sunglasses: 
Australia: AUD$160
Hong Kong: HK$800
New Zealand: NZ$175
Singapore: SG$150
Rest of the World: US$160