Getting Query To Display Only 150 And 162 As They Have Purchased Only One Product?

Is there a way to find customers purchased only single product from the following table?

cusno Product Date
----- ------ ----
121 ES 03/12
121 NT 30/12
131 ST 03/12
13 WT 04/12
150 ES 05/12
150 ES 06/12
150 ES 07/12
160 MN 05/12
160 ES 06/12
160 ES 07/12
162 NT 08/12

I need a query to display only 150 and 162 as they have purchased only one product.