Alcantara is a patented brand-name type of microfiber made in Italy, that is used for automotive aplications (among other things) because its fire retardant, washable, lighter than leather and less hot under the sun, more grippy, and has a premium look similar to suede leather but more durable and resistant to wear.
There are different qualities, though supposedly Porsche's is high quality and more durable than others though wear quicker than natural leather I believe (I have heard mixed opinions).
Areas such as the steering wheel and shift knob in manuals are the parts that wear quicker due to the contact with hands, but then again they are areas that are not to hard too replace if need be, so IMO well worth getting if you like it more than natural leather, and personally it looks much much much better than full leather interior, IMO getting full leather on a sportcar when an alcantara version is available is a shame, kind of like putting a cover on a leather sofa so it lasts longer ... unless you actually like better the look of natural leather, thats different then.
Not that it can be considered long time but I have 8,000km on my GTS and all the alcantara bits are 100% as new, including the wheel.
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⇒ Carlos - Porsche 991 Carrera GTS