Which feature of the MSA G1 SCBA helps ensure a secure fit of the facepiece?

The feature that ensures a secure fit of the facepiece on the MSA G1 SCBA is the customizable features. This aspect of the equipment allows users to adjust and tailor the facepiece to better fit their facial structure. A proper fit is crucial for maintaining the effectiveness of respiratory protection, as it minimizes any potential gaps where contaminants could enter. The ability to customize various components contributes significantly to comfort and safety, making it easier for the user to perform their duties without concerns regarding the integrity of the breathing apparatus.