Mariana T. Buttermilch (asker) Nov 29, 2016:

Thanks Liz, thanks Favio, now my question sounds pretty silly!!!

liz askew Nov 29, 2016:

Indeed:) don't go too deep, although at least you are an observant consumer, so you are an aware one at that!

Mariana T. Buttermilch (asker) Nov 29, 2016:

Thanks Liz, I guess I went too deep in my analysis I understand that they promise sth., but what if they use materials from a third company, are they really sure they won't fail either? Ok, I do understand that I have to translate it literally!!!

liz askew Nov 29, 2016:

Well, the phrase does seem to be used, from WIKI
Defects In Materials and Workmanship[edit]
The most common kind of warranty on goods is a warranty that the product is free from defects in materials and workmanship. This simply promises that the manufacturer properly constructed the product, out of proper materials. This implies that the product will perform as well as such products customarily do.

It is common for these to be limited warranties, limiting the time the buyer has to make a claim. For example, a typical 90-day warranty on a television gives the buyer 90 days from the date of purchase to claim that the television was improperly constructed. Should the television fail after 91 days of normal usage, which because televisions customarily last longer than 91 days means there was a defect in the materials or workmanship of the television, the buyer nonetheless may not collect on the warranty because it is too late to file a claim.

Mariana T. Buttermilch (asker) Nov 29, 2016:

@ Fabio, gracias amigo, pero ese es mi planteo nadie puede garantizar que lo que fabrica estará libre de defectos por un año, algo puede fallar en el dispositivo que venden y por eso dan una garantía por un año