The throat size is determined by the wall thickness.
Common wall compositions and their throat size:

  • 2-1/2” metal stud, 1 layer of 5/8” sheetrock both sides: 3-3/4”
  • 3-5/8” metal stud, 1 layer of 5/8” sheetrock both sides: 4-7/8”
  • 3-5/8” metal stud, 2 layers of 5/8” sheetrock both sides: 6-1/8”
  • 6” metal stud, 1 layer of 5/8” sheetrock both sides: 7-1/4”
  • 8” block: 7-3/4″