Hi, I work in a retail bakery. Today while organizing my icing tips, I found a plethora of these U or C-shaped tips (seems like #79, #80, or #81). I have a whole bunch and I'd love to start using them! What techniques are they used for? Is there a specific name for this kind of tip? Thank you!

Search for White Flower Cake Shoppe flower.

^^^^ yup...makes cupped petals.

Those are the Wilton "chrysanthemum (mum)" tips.  From small to large:  79, 80, 81

Here is a tutorial on the Wilton site:

http://www.wilton.com/technique/Chrysanthemum-Mum  

The recent cake craze is to use the HUGE version of a mum tip (different appearance, same result, only HUGE.  The Wilton version of the huge mum tip is discontinued, but you can get the tip from other sources online. 

http://shop.whiteflowercake.com/products/the-white-flower-cake-shoppe-signature-flower  

http://www.amazon.com/Ateco-Decorating-Tip-401/dp/B0000VLE3Q  

http://www.amazon.com/gp/product/B00DR0EU4C/ref=pd_lpo_sbs_dp_ss_2?pf_rd_p=1944687562&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B0000VLE3Q&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0CQ2DCV0ET52AZG6VY51  

http://www.amazon.com/Decopac-Ateco-Ruffle-Tip-403/dp/B008GUYI72/ref=pd_bxgy_79_text_y