I buy the most expensive one Costco sells because it is pretty large. We use it in our shop almost daily. Many people don't realize that most items you buy from Costco except for electronics are garanteed for as long as you have a costco card. I have been doing this since Costco came to San Antonio in 2001 and I have went through 4 or 5 of them. They ask no questions and give me the option of my money back or getting a different one. They do require the original invoice.