Must be trimmed to size. Frequently difficult to make fit correctly. Always use a steel tape and recheck measurements for accuracy. Installation requires only a few basic tools, provided pre-assembly is done at the factory and all necessary hardware is included with your order. You will be thankful for their advise and assistance.
Reliable companies offer product samples on request and a reference list of customers.
Affiliation with the Better Business Bureau and similar agencies is a plus. About 45 working days is a reasonable time from order to shipping. A lifetime warranty is of little value if a product is poorly designed or poorly made in the first place. Look for a good and reasonable warranty without lots of disclaimers and exclusions from an established company that will be available should you need warranty service.