The best racks imo are the Magic Ball Racks. These are the template racks for about $10.
The best triangle conventional rack is the Delta 13-Elite. If you don't want to spend $100 for this, the next best imo is the one below:
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http://www.seyberts.com/products/Black_Beauty_8_Ball_Rack-100172-298.html
This one is less than $10, and it is made of THICK plastic. I think this one is better than the Diamond Wood rack that is about $50. We have this rack in a local pool hall, and they have held up great for 20 years. The wood ones fall apart well before that.
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Whatever you do, don't get this rack! This is the cheapest, it flexes like crazy. One pool hall had all of these. You don't want this one.
http://www.seyberts.com/products/Plastic_Ball_Racks-2287-298.html