Laboratory Screw Joints

The GL thread is the most common thread on lab equipment made of glass. BOLA offers a modular construction system with many different components with GL threads. All components can be combined and thus allow an easy transition from glass to plastic accessories.

Using BOLA Laboratory Screw Joints you can simply connect tubes or tubing made of glass, metall or plastics directly to GL threaded sockets, no matter whether it is an reactor lid made of glass or a BOLA GL-Fitting in PTFE or a bottle distributor made of PP.

Comprising a sealing ring, a tapered ring and a v-ring, BOLA Laboratory Screw Joints provide a tight connection which is suitable for pressure and vacuum applications.

Furthermore, by exchanging the inner parts only, tubing with different outer diameters can be connected to the same GL thread. This way you can connect e. g. to a GL 14 thread tubing with an outer diameter from 0.8 to 8.00 mm. This system allows also to use BOLA GL Fittings for the assembly of a tubing reduction.

A  GL Tube Fitting
B  Laboratory Screw Joint
C  Laboratory Screw Joint
D Laboratory Screw Joint








GL screw joints system up to 5 bar

A  Threaded neck of fitting
B  Tapered ring
C  V-ring
D  Nut
E  Tubing or tube




1. Push the nut on the tubing/tube
2. Push V-ring and then the tapered ring on the tubing/tube
3. Tighten the nut on the threaded neck – ready
This economic screw joint system was developed especially for tubing made of PTFE, PFA or FEP, but it can also be used with tubes made of glass or steel. Its function is based on compression rings which provide a pressure resistance of up to 5 bar at room temperature. All parts which are exposed to the medium are made of PTFE. Only the nut which is not in contact with the medium is made of glass-fibre reinforced PTFE for better stability. The fittings and nuts have metric threads.
All components of this system have a universal chemical resistance, since the product is only exposed to PTFE.