What's the best backpack sprayer?

[River Parish Lawn Care]

Looking for suggestions for a quality commercial grade backpack sprayer. It will be used solely for applying herbicides.

Thanks!

[2_Djinn]

No complaints with my Solo. It has been very soild.

[ArizPestWeed]

I've got 10 SP-3 , the best so far.
Solo has many leak problems from the lids .
I sent 4 back to the factory and they sent me 4 new ones , same thing , trashed 'em.
http://www.tessmanseed.com/ they have the best deals

[TURF DOCTOR]

We have run sp for years no problems with them try northern tool