The Northwest Passage personalized Chums.  
 
Three sizes: Regular, Large and Small. Regular fits most.  Chose small for reading or daily glasses. Chose large for large  frame sunglasses. 
Guide approved.
 
From Chums: 
 
The easily adjustable Chums Original retainer is the product that put us on the map. Millions agree that our Original retainer is ideal for all adventures! Whether you're on water, land, snow, or in the air, this retainer has it all—quality, comfort, and the ability to fit most standard frames.
 
Bead adjusts for superb fit
Weight without packaging: 0.4 oz.
Length: 14.5"
Hand wash with mild soap. Rinse thoroughly. Stretch to original length.
Made in the USA