I have a synthetic stuffed long Kelty sleeping bag. In its stock sack the bag measures about 19" high by 10" wide but when I sit on it I can compress the sack to ~2/3 the height. Which size of eVent sack could effectively compress my bag the most? Thanks.

Tech Specs:

Material:

eVent 

Closure:

Roll-top with compression straps 

Volume:

[XS] 6/2L; [S] 10-3.3L; [M] 14/4.5L; [L] 20/6.7L; [XL] 30/10L 

Dimensions:

[XS] 6 x 14in; [S] 7 x 16in; [M] 8 x 18in; [L] 9 x 20in; [XL] 10.5 x 23in 

Backpack Straps:

No 

Weight:

[XS] 3.7oz; [S] 4.5oz; [M] 5.2oz; [L] 5.9oz; [XL] 7.4oz 

Warranty:

1 Year 

Country of Origin:

China