This one fiber optic adapters are used in connecting fiber optic connectors, it is called Hybrid fiber optic adapter when the opposite connectors are different.

Features           
High size precision
Good interchangeability
Good duplication
Good resistance to wear
Good temperature characteristic 

Applications
Optical fiber communications system
Optical instruments measuring appliance
Optical fiber CATV
Optical fiber sensor

Specification
Insertion Loss:
PC/SM: below 0.2dB
PC/MM: below 0.3dB
PC/UPC: below 0.15dB
PC/APC: below 0.2dB

Return Loss:
PC:  above 50dB 
APC: above 65dB

Exchangeability:   below 0.1dB
Tensile strength:   bove 100N
Durability: 1000times
Operating temperature: 45 to 80 degree Celsius

AVAILABILITY:
Simplex/Duplex adaptor available
Different mateiral available
SM/MM available
Various type