diff --git a/src/dual.jl b/src/dual.jl
index aadc58e..e39c5c6 100644
--- a/src/dual.jl
+++ b/src/dual.jl
@@ -3,6 +3,11 @@ dual(x) = x
 nondual(r::AbstractUnitRange) = r
 isdual(::AbstractUnitRange) = false
 
+dual_type(x) = dual_type(typeof(x))
+dual_type(T::Type) = T
+nondual_type(x) = nondual_type(typeof(x))
+nondual_type(T::Type) = T
+
 using LabelledNumbers: LabelledStyle, IsLabelled, NotLabelled, label, labelled, unlabel
 
 dual(i::LabelledInteger) = labelled(unlabel(i), dual(label(i)))
diff --git a/src/gradedunitrange.jl b/src/gradedunitrange.jl
index 37cda65..487552c 100644
--- a/src/gradedunitrange.jl
+++ b/src/gradedunitrange.jl
@@ -90,6 +90,10 @@ Base.eltype(::Type{<:GradedUnitRange{T}}) where {T} = T
 LabelledNumbers.label_type(g::AbstractGradedUnitRange) = label_type(typeof(g))
 LabelledNumbers.label_type(T::Type{<:AbstractGradedUnitRange}) = label_type(eltype(T))
 
+sector_type(x) = sector_type(typeof(x))
+sector_type(T::Type) = error("Not implemented")
+sector_type(T::Type{<:AbstractUnitRange}) = label_type(T)
+
 function gradedrange(lblocklengths::AbstractVector{<:LabelledInteger})
   brange = blockedrange(unlabel.(lblocklengths))
   lblocklasts = labelled.(blocklasts(brange), label.(lblocklengths))
diff --git a/src/gradedunitrangedual.jl b/src/gradedunitrangedual.jl
index 78cf48e..2d26d91 100644
--- a/src/gradedunitrangedual.jl
+++ b/src/gradedunitrangedual.jl
@@ -9,6 +9,21 @@ nondual(a::GradedUnitRangeDual) = a.nondual_unitrange
 dual(a::GradedUnitRangeDual) = nondual(a)
 flip(a::GradedUnitRangeDual) = dual(flip(nondual(a)))
 isdual(::GradedUnitRangeDual) = true
+
+function nondual_type(
+  ::Type{<:GradedUnitRangeDual{<:Any,<:Any,NondualUnitRange}}
+) where {NondualUnitRange}
+  return NondualUnitRange
+end
+dual_type(T::Type{<:GradedUnitRangeDual}) = nondual_type(T)
+function dual_type(type::Type{<:AbstractGradedUnitRange{T,BlockLasts}}) where {T,BlockLasts}
+  return GradedUnitRangeDual{T,BlockLasts,type}
+end
+function LabelledNumbers.label_type(type::Type{<:GradedUnitRangeDual})
+  # `dual_type` right now doesn't do anything but anticipates defining `SectorDual`.
+  return dual_type(label_type(nondual_type(type)))
+end
+
 ## TODO: Define this to instantiate a dual unit range.
 ## materialize_dual(a::GradedUnitRangeDual) = materialize_dual(nondual(a))
 
diff --git a/src/labelledunitrangedual.jl b/src/labelledunitrangedual.jl
index 319521e..b2ca841 100644
--- a/src/labelledunitrangedual.jl
+++ b/src/labelledunitrangedual.jl
@@ -14,9 +14,23 @@ label_dual(::IsLabelled, a::LabelledUnitRangeDual) = dual(label_dual(nondual(a))
 isdual(::LabelledUnitRangeDual) = true
 blocklabels(la::LabelledUnitRangeDual) = [label(la)]
 
+function nondual_type(
+  ::Type{<:LabelledUnitRangeDual{<:Any,NondualUnitRange}}
+) where {NondualUnitRange}
+  return NondualUnitRange
+end
+dual_type(T::Type{<:LabelledUnitRangeDual}) = nondual_type(T)
+function dual_type(T::Type{<:LabelledUnitRange})
+  return LabelledUnitRangeDual{eltype(T),T}
+end
+
 LabelledNumbers.label(a::LabelledUnitRangeDual) = dual(label(nondual(a)))
 LabelledNumbers.unlabel(a::LabelledUnitRangeDual) = unlabel(nondual(a))
 LabelledNumbers.LabelledStyle(::LabelledUnitRangeDual) = IsLabelled()
+function LabelledNumbers.label_type(type::Type{<:LabelledUnitRangeDual})
+  # `dual_type` right now doesn't do anything but anticipates defining `SectorDual`.
+  return dual_type(label_type(nondual_type(type)))
+end
 
 for f in [:first, :getindex, :last, :length, :step]
   @eval Base.$f(a::LabelledUnitRangeDual, args...) =
diff --git a/test/test_basics.jl b/test/test_basics.jl
index 96e7dc6..cbd9bc4 100644
--- a/test/test_basics.jl
+++ b/test/test_basics.jl
@@ -13,7 +13,13 @@ using BlockArrays:
   combine_blockaxes,
   mortar
 using GradedUnitRanges:
-  GradedOneTo, GradedUnitRange, OneToOne, blocklabels, gradedrange, space_isequal
+  GradedOneTo,
+  GradedUnitRange,
+  OneToOne,
+  blocklabels,
+  gradedrange,
+  sector_type,
+  space_isequal
 using LabelledNumbers:
   LabelledUnitRange, islabelled, label, labelled, labelled_isequal, unlabel
 using Test: @test, @test_broken, @testset
@@ -41,6 +47,7 @@ end
     gradedrange(["x" => 2, "y" => 3]),
   )
     @test a isa GradedOneTo
+    @test sector_type(a) === String
     @test labelled_isequal(a, a)
     @test !labelled_isequal(a0, a)
     @test !labelled_isequal(a, a0)
diff --git a/test/test_dual.jl b/test/test_dual.jl
index 8c4370e..179e71e 100644
--- a/test/test_dual.jl
+++ b/test/test_dual.jl
@@ -14,8 +14,8 @@ using BlockArrays:
   mortar,
   combine_blockaxes
 using GradedUnitRanges:
-  GradedUnitRanges,
   AbstractGradedUnitRange,
+  GradedUnitRanges,
   GradedUnitRangeDual,
   LabelledUnitRangeDual,
   OneToOne,
@@ -23,11 +23,14 @@ using GradedUnitRanges:
   blockmergesortperm,
   blocksortperm,
   dual,
+  dual_type,
   flip,
-  space_isequal,
   gradedrange,
   isdual,
-  nondual
+  nondual,
+  nondual_type,
+  space_isequal,
+  sector_type
 using LabelledNumbers:
   LabelledInteger, LabelledUnitRange, label, label_type, labelled, labelled_isequal, unlabel
 using Test: @test, @test_broken, @testset
@@ -70,7 +73,8 @@ end
   @test !isdual(la)
   @test labelled_isequal(la, la)
   @test space_isequal(la, la)
-  @test label_type(la) == U1
+  @test label_type(la) === U1
+  @test sector_type(la) === U1
 
   @test iterate(la) == (1, 1)
   @test iterate(la) == (1, 1)
@@ -90,7 +94,13 @@ end
   @test isdual(lad)
   @test nondual(lad) === la
   @test dual(lad) === la
-  @test label_type(lad) == U1
+  @test label_type(lad) === U1
+  @test sector_type(lad) === U1
+
+  @test dual_type(la) === typeof(lad)
+  @test dual_type(lad) === typeof(la)
+  @test nondual_type(lad) === typeof(la)
+  @test nondual_type(la) === typeof(la)
 
   @test iterate(lad) == (1, 1)
   @test iterate(lad) == (1, 1)
@@ -155,6 +165,7 @@ end
     @test eltype(ad) == LabelledInteger{Int,U1}
     @test blocklengths(ad) isa Vector
     @test eltype(blocklengths(ad)) == eltype(blocklengths(a))
+    @test sector_type(a) === U1
 
     @test space_isequal(dual(ad), a)
     @test space_isequal(nondual(ad), a)
@@ -163,6 +174,11 @@ end
     @test !space_isequal(a, ad)
     @test !space_isequal(ad, a)
 
+    @test dual_type(a) === typeof(ad)
+    @test dual_type(ad) === typeof(a)
+    @test nondual_type(ad) === typeof(a)
+    @test nondual_type(a) === typeof(a)
+
     @test isdual(ad)
     @test !isdual(a)
     @test axes(Base.Slice(a)) isa Tuple{typeof(a)}