Letters concerning inquires should be clear, specified to the point.
State clearly what information you need. Be it a catalogue, a price list, an estimate, a quotation, a specimen or a sample.
Write specifically about the design, size, shape, price, and quantity, quality etc. about the product or service in which you are interested.
Be brief to the point in your inquiry. Once you have said what you want, stop there and finish your letter.
All inquiries should be promptly and carefully replied. It is discourteous to keep an inquiry for long. This can annoy your customer which means a loss in your business