For the price, go for it. I fixed up an old guitar which was falling apart, and these are good replacements. Mostly because it is going to be a travel guitar.
But quality is not really up top. The 'black' screws, scratch easily which makes the silver color of the original screws visible, and the metal bends easy. In my case this was a good thing because i had a really stubborn machine head, but if you force these tuning knobs onto your guitar and they bend, you may end up with a gap or two.
Anyways, for the price: Definite buy. Do you want to replace the ones in your "proper" guitar, get some more premium ones.