This refers to the type and size of a light globe base.
E27 is the most common type of Edison Screw base, It is often referred to as just ES.
The number '27' refers to the diameter.
This type of base is also compatible with Compact Fluorescent, LED and Smart Globes
See the table below for more details.
|E05 E5||018 ≤18||05 mm||Lilliput Edison Screw (LES)|
|E10||030 ≤30||10 mm||Miniature Edison Screw (MES)|
|E11||120/240 240/120||11 mm||Mini-Candelabra Edison Screw (mini-can)|
|E12||120||12 mm||Candelabra Edison Screw (CES)|
|E14||240||14 mm||Small Edison Screw (SES)|
|E17||120||17 mm||Intermediate Edison Screw (IES)|
|E26||120||26 mm||[Medium] (one-inch) Edison Screw (ES or MES)|
|E27||240||27 mm||[Medium] Edison Screw (ES)|
|E39||120||39 mm||(Mogul) Giant Edison Screw (GES)|
|E40||240||40 mm||(Mogul) Giant Edison Screw (GES)|