The bottle charm measures about 1" high, .5" wide.
"Felix Felicis (IPA pronunciation: \/'fiːlικs fə'lıʃıs\/, \/feːliks feːlikis\/ Classical Latin: FELIX•FELICIS) is a potion that makes the user incredibly lucky. The name is derived from Latin, although it is grammatically nonsensical, translating to "the luck of the lucky". It is described as looking like molten gold and bubbling. The potion also helps the person know what to do and where to go. Extremely difficult to brew, if the potion is used too often, it will affect the user's ability to tell what is humanly possible and what is not, as well as inducing toxic effects to those who ingest it excessively. Felix Felicis is banned in organized activities such as sporting events and examinations.
The potion is based on Rowling's own personal philosophy. When asked on her website whether or not she believes in fate, Rowling responded, "No, I believe in hard work and luck, and that the first often leads to the second." Rowling feels that Felix best exemplifies this philosophy, as it is the user's confidence in himself that leads to his being "lucky" and the user's hard work that leads to a creation of pure luck.
Professor Slughorn offers a small bottle of Felix Felicis as a prize in a potion-brewing contest. Harry wins it with the hints written in the mysterious Half-blood Prince's textbook. The potion is eventually used in anti-Voldemort activities, but not before Harry tricks Ron into believing that he's given the potion to him right before a Quidditch match, eliminating the self-doubt problem that had crippled Ron's playing skills" - Wikipedia article
This botle comes from the sixth Harry Potter book.