Adapter 1  (39mm)

It fits:

• Medela
• Dr Brown's Narrow Neck
• Pigeon Narrow Neck 
• Pigeon Narrow Neck (Glass Bottle)
• Nanobebe Narrow Neck
• Chicco 
• & Most other narrow neck bottles.

Adapter 2 - (56mm)

It fits:

• Dr Brown's Wide Neck

Adapter 3 - (60 mm)

It fits:

• Tommee Tippee Wide Neck

Adapter 4 - (53mm)

It fits:

• MAM
• Pigeon Wide Neck

Adapter 5 - (50mm)

It fits:

• NUK (Nature Sense) 

Baby Bottle Brands that are compatible with PRO warmer 2.0 (They DO NOT require adapters, fits straight into the warmer):

• AVENT
• Chicco
• Lansinoh
• Combi
• Dodie
• Spectra
• Richell
• Snowbear
• DoubleHeart
• Bebe Confort