i'm 5,8 slim. do i need to wear small or med?

Tech Specs:

Material:

[shell] Gore-Tex Performance Shell (2-layer); [lining] taffeta mesh, brushed tricot 

Fabric Waterproof Rating:

guaranteed waterproof 

Fabric Breathability Rating:

guaranteed breathable 

Hood:

yes, fixed 

Fit:

AK (performance oriented, articulated) 

Length:

hip 

Venting:

underarm zip vents 

Powder Skirt:

yes, removable 

Pockets:

2 hand-warmer, 1 napoleon 

Seams:

fully taped (Gore-Tex 13mm) 

Wrist Gaiters:

no 

Liner-Compatible:

no 

Recommended Use:

snowboarding 

Manufacturer Warranty:

lifetime