Basic Tapers:

In a 2½ thick brick a            
#1 Arch tapers from 2½" to 2 ⅛"
#2 Arch tapers from 2½" to 1¾"
#3 Arch tapers from 2½" to 1"

In a 3” thick brick a
#1 Arch tapers from 3” to 2 ¾”
#2 Arch tapers from 3” to 2 ½”
#3 Arch tapers from 3” to 2”
#4 Arch tapers from 3” to 1”                                        

In 2½" thick brick a             
#1 X Wedge tapers from 2½" to 2¼"                               
#1 Wedge tapers from 2½" to 1⅞"                  
#2 Wedge tapers from 2½" to 1½"

In a 3" thick brick a
#1 Wedge tapers from 3" to 2¾"                     
#2 Wedge tapers from 3" to 2½"                                     
#3 Wedge tapers from 3" to 2"

View of basic firebrick tapers

Straights come in many different sizes including:
9x4.5x2.5, 9x4.5x3, 9x6.75x2.5, 9x6.75x3, 12x4.5x2.5, 12x4.5x3, 12x6x2.5, 12x6x3, 12x9x2.5, 12x9x3, 12x12x1.5, 12x12x2,12x12x3, 13.5x4.5x2.5, 13.5x4.5x3, 13.5x6x2.5, 13.5x6x3, 13.5x9x2.5, 13.5x9x3, 18x4.5x2.5, 18x4.5x3, 18x6x2.5, 18x6x3, 18x9x2.5, 18x9x3, 18x12x2, 18x12x2.5, 18x12x3 and many more!