What is the following parts of your query supposed to be checking?

WHERE @category = 'hardware'

AND @series = '1500'

AND @diameter = '5"'

AND @type = 'caster'

@category is a variable, which I am assuming is set somewhere above the code you showed us. This part of each query is not checking anything in the table, and if you have done the following:

DECLARE @category char(8);

SET @category = 'hardware';

Then, that criteria will be true for every single row. I think what you really wanted was something like:

WHERE category = @category

AND series = @series

AND diameter = @diameter

AND type = @type

...

Change the columns to the actual column names in your query.