Filter product by height, length and width.

Hello,

I thought this would be really easy but I can't get it to work.

I want customers to be able to filter products by their height, length or width using the data from the product information, the fields just after the weight field on the backend product listing.

I tried creating a custom field label height and sql query:

select product_height from josii_hikashop_product

Along with numerous variations but nothing works.

I tried creating a new filter > Single drop down > Product Information > Height but this does nothing either.

Suggestions gratefully received.

Thanks!