Each type of tip (round, star, petal, etc.) has a number range. For example round tips start in the 0’s and go up to 12 and larger. Find one that suits your piping application.
With the exception of the Rose all of the following tips are meant to be fit with a coupler, ring, and pastry bag. Different brands of tips, like Ateco and Wilton, use the same numbering system for their tips and are interchangeable.
See the following links for a full selection of tips: (WILTON brand)
http://search.wilton.com/?q=tips and (ATECO brand)
http://www.cakedeco.com/cgi-bin/webc.cgi/st_main.html?p_catid=242&page=1BASIC PIPING APPLICATIONSLines and InscriptionsRound tip (# 0-12) or pastry cone
RosettesStar tip (# 16-18, 27…)
Shell BorderStart tip (# 16-18, 27…)
DotsRound tip (# 1-12)
Bead BorderRound tip (# 1-12)
MISCELLANEOUS PIPING APPLICATIONSCrazy Curls or Cornelli LaceRound tip (# 1-5) or pastry cone
Rickrack BorderPetal tip (# 102-104) or Flat tip (# 44 or 45)
Crazy BorderAny Petal, Round, or Star tip
Cloud BorderRound tip (# 6-12)
Ruffled Ribbon Border and Ruffled Swags
Petal tip (# 102-104)
Flat RibbonPetal tip (# 102-104) or Flat tip (#44 or 45)
Thread SwagsRound tip (# 1-5)
Fabric SwagsChrysanthemum tip (#79 or 81)
Spiral SwagsStar tip (# 16-18, 27…)
LatticeFlat tip (# 45)
PlaidAssortment of Flat and Round tips (# 42 or 89 multi-openings, 44 or 45 flat, 1-8 round)
BowsPetal tip (# 102-104)
Basket weaveBasket weave tip (#46-48 range)
FLOWERS and LEAVESSome of the following flowers, in addition to the piping tips, may need a pastry cone or small round tip filled with tinted buttercream or chocolate to pipe details like flower centers, dots, seeds, etc.
Roses
Large Petal tip (# 125)
Miniature or Tea RosesPetal tip (#103-104)
BudsPetal tip (#103 or 104)
PoppiesPetal tip (#103-104)
Blossoms, Daffodils, Violets, and PansiesPetal tip (#104)
Daisies, Coneflowers, and Black Eyed Susan’s (Full and Perspective)
Petal tip (#103-104) or Round Tip (#5-8)
ChrysanthemumsMum tip (#79 or #81)
Lilies
Leaf tip (#352)
SunflowerLeaf tip (# 352) or can substitute Leaf tip (# 67)
HydrangeaPetal tip (# 102 or # 103)
GrapesRound Tip (#5-12)
GrassMulti opening tip (#233) or Round tip (#3-8)
LeavesLeaf tip (# 352 or # 65-68)