There is no stretching material around the arm with black and white stripes that kinda look like elastic.  Only around the neck is elastic

It is Black.  still brand new.  It was in the box ever since 1982.  Haven't been wash nor worn except trying it on once, too small.

Size: Small

Pit-to-pit: 15inches

Pit to sleeve: close to 6 inches

Back top to bottom: close to 26 inches.

Only accept return if it doesn't fit you, but please don't return it if you gonna wash it.