Kastle TX90 184 cm c/w Salomon MTN pin bindings, skins & ski crampons, £650

Moderately used skis and bindings, come with Contour hybrid skins & 90 mm Dynafit ski crampons. 
Each ski w/binding 1792g, each skin 246 g
Bindings fitted to suit Mondo 27.5 313mm sole length; 17mm further enlargement possible, or reposition binding

Are these stiff enough to ski steep terrain?

Well Carlo they are adequately stiff to provide edge hold. They are a touring ski so they are light and also have some vibration dampening; ultimately skier ability is a determining factor, these are skis not damp noodles. 

Ski choice is a rational compromise that depends on the proportion of skinning skiing the terrain condition and types. With primary lift access you may concede some weight e.g. SHIFT binding + a robust ski to tackle gnarly terrain, but if you have to skin and only ski occasional steep pitches these skis are adequate.