diff --git a/Readme.md b/Readme.md
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+++ b/Readme.md
@@ -11,6 +11,8 @@
 
 :warning: **WARNING : _Please don't use a 3D printed canister (or even our mask) in life threatening situations !_** :warning:
 
+This canister is made to be used with mask supporting standard 40mm threaded canisters - sometimes also known as "_nato threaded_" canisters - which the standard dimensions are defined in [sources/nato_thread_spec.png](./sources/dimension/nato_thread_spec.png).
+
 This filter canister works by holding a filtering material - _usully activated charcoal_ - in between two securelly held mask/filter pieces.
 
 The center sleeve is made to hold both the mask/filter pieces, using the pressure of the two outer shell part being screwed in together around the sleeve.