fake nails..? whats 'full set' and 'orginal acrylic nails'

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hey ladies.. I'm new to this fake nails thing and I see in some stores they have full set but like last year I got the original acrylic nail.. what's the difference? I really don't want to pay so much cause I paid the original acrylic nails for $20 and the full set is $17.99. whats the difference ?

added: also isn't coffin style, bellerina, etc are different prices? so so far I see full set so that must be the original style and if you want something else is more pricey...

Also isn't the original set tips are thick?