GL Threads

GL threads are externally threaded glass fittings.
They come in a range of sizes, some simply tooled on borosilicate tubing, some molded on bottles.
The inside diameters show the maximum passthrough.
There are closed caps, open caps, septum seals, and sealing rings for all sizes.
The sealing rings accommodate tubes or electrodes at nominal diameter ± ~ 1 mm.

Dimensions in millimeters.

Size  ID tube (bottle) OD 

Available sealing IDs

GL14 8.5 12 6
GL18 10.5 16 6, 8, 10
GL25 (tube) 18 22 8, 10, 12
GL25 (25 ml bottle) 14.3 (36) 8, 10, 12
GL32 (tube) 24 28 10, 12, 14, 16, 18
GL32 (50 ml bottle) 17 (46) 10, 12, 14, 16
GL45 (tube) 35 40 26, 32
GL45 (100 ml bottle) 30 (55) 26, 32
GLS80 (500 ml bottle) 65 (102)  

 

Some of the ways of connecting with GL threads are shown here for GL14 options; the larger sizes have similar possibilities.
There are teflon inserts for GL14 that hold and seal 
1.6 mm (1/16"), 3 mm, 3.2 mm (1/8"), and 6 mm tubes or electrodes.

GL14 closures & connections

 

GL14 with tube through sealing ring

Closed up tight