The FAA is adopting a new airworthiness directive (AD) for all Stemme GmbH (Stemme) Model Stemme S 12 gliders. To address the unsafe condition, Stemme published service material to provide replacement instructions for affected copper sealing rings, and a parts installation restriction. (c) Applicability This AD applies to all Stemme GmbH Model Stemme S 12 gliders, certificated in any category. Note 1 to paragraph (c): All of the affected airplanes were produced and delivered with the affected copper sealing rings installed. (ii) [Reserved] (3) For Stemme material identified in this AD, contact Stemme GmbH, Flugplatzstrasse F2 Nr.