Boiler Sight Glass

I have 15mm OD x 2mm wall Acrylic tube.
I have a 15mm compression fitting.
Do I gently use a brass "olive", do I wrap a load of PTFE tape in place of the "olive" or is there another option?
Seems a suitably sized Silicon seal would be an answer, but where to source it?

[graysalchemy]

Push fit fittings would be better like

That is what cnelsonplumber recommended on his how to on Another Site.

[Joe1002]

My last boiler I used one of them but it cannot be removed.
I now use jg fittings with a s/s elbow and the s/g can be removed in seconds if needed for extra cleaning.
http://www.wickes.co.uk/Speedfit-Male-C ... n/p/160115

Thanks GA, it's something I should have thought of!

they look the business i might build this myself

Just tried it, the standard compression olive does the job well!