Size Comparison

Shasta

Expanded Dimensions: 20"H x 10"W x 6.5"D
Stuff Sack Dimensions:  9"H x 9"W x 3.5" D
Capacity: 21L
Weight: 15oz 

Mayfly
Expanded Dimensions: 18"H x 9"W x 5"D
Stuff Sack Dimensions: 8"H x 7.5"W x 3"D
Capacity: 14L
Weight: 12oz