How weights work
Probability of an option is weight ÷ sum of weights. A list of Common (5), Uncommon (3), Rare (1) gives Rare a 1-in-9 chance. The winner is still chosen with cryptographic randomness — only the distribution changes.
Honesty
If you run a public giveaway with uneven odds, say so. Hidden weights on a wheel that looks equal would be a different product. Here the slices grow with the weight so the picture matches the math. Details are on the randomness page.