The
"HC Series batteries were designed to give you the option
of 4 different capacity ratings capable of fitting into one
battery enclosure. A.9-inch door spacer is all that is required
for the HC1217W and HC1221W Series batteries to be completely
interchangeable. This unique design allows you to offer 4
different models while only paying for one common tooling
design. The resulting toolings savings can be in the hundreds
of thousands of U.S. dollars.