Answer:
A clear statement of the desired action
Step-by-step explanation:
A claim letter, often referred to as a letter of complaint, is a type of persuasive letter sent by a customer to a business or agency to report an issue with a product or service in order to seek the correction of the said issue. When the remedy is obvious, a claim letter usually opens with a statement of the desired action (e.g. refund, replacement). When the situation is not as clear, a paragraph explaining the problem first should be included.
In the given case, the remedy is obvious, so the opening for a claim letter would be: Please send me a full refund for the Stratus Balance Ball I recently purchased on your website.