What Is Default Behavior Of Select Box - Text

I want a product Feature that is chosen by the customer using a Select Box drop down in the front-end filter. Am I configuring this properly?

Feature Setup:

Name: Compressor Type

Feature Type: Select Box - Text

Two Variants: Type 1, Type 2

Filter setup:

Name: Compressor Type

Filter by: Compressor Type
Display Type: Expanded
When I view the Category for the products it has the Compressor Type filter shown but the choices are check boxes not a select box drop down.
I have a product_filters_variants.override.tpl file created a long time ago (version 2 or 3) for displaying Manufacturer as a Product Feature and front-end checkbox filter. But, even when I disable it and ctpl and cc I only get check boxes for the Compressor Type filter.