50mm f1.8

Hi all, i'm thinking of getting the Canon 50mm f1.8 lense for my T3i.  I'm just wondering if there are other brands of this type of lense?  I went to Tamron and Sigma's site but I didn't see any.  i'm hoping another brand would be better built as I heard the Canon version of this lense is not well built in terms of construction.  thanks.

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http://500px.com/baneling
Canon T3i
Canon EF-S 18-55mm f/3.5-5.6 IS
Canon EF-S 55-250mm f/4-5.6 IS