Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_2071644_2 ( weight__kg_m_ VARCHAR, flange_width__mm_ VARCHAR )

### Question ###
How many weights are there when the flange with is 304?

### Accurate SQL ###

SELECT COUNT(weight__kg_m_) FROM table_2071644_2 WHERE flange_width__mm_ = 304