Happy Birthday Round Letter Candles in Holders. Birthday Letter Candles each measure approximately 5cm (2″) in height and come in assorted colours. Cake toppers spell out “Happy Birthday,” making them ideal for decorating cakes, cupcakes and other baked goods at any birthday party. Happy Birthday candles can be used alone, or mixed with other coloured candles, number candles or cake bunting for extra festive flair.