diff --git a/src/custom-sort/custom-sort-types.ts b/src/custom-sort/custom-sort-types.ts
index b9461d2..5dea555 100644
--- a/src/custom-sort/custom-sort-types.ts
+++ b/src/custom-sort/custom-sort-types.ts
@@ -13,14 +13,10 @@ export enum CustomSortGroupType {
 
 export enum CustomSortOrder {
 	alphabetical = 1,  // = 1 to allow: if (customSortOrder) { ...
-	alphabeticalLowerFirst,
-	alphabeticalUpperFirst,
 	alphabeticalWithFileExt,
 	trueAlphabetical,
 	trueAlphabeticalWithFileExt,
 	alphabeticalReverse,
-	alphabeticalLowerFirstReverse,
-	alphabeticalUpperFirstReverse,
 	alphabeticalReverseWithFileExt,
 	trueAlphabeticalReverse,
 	trueAlphabeticalReverseWithFileExt,
diff --git a/src/custom-sort/custom-sort.ts b/src/custom-sort/custom-sort.ts
index 976e834..97d81ae 100644
--- a/src/custom-sort/custom-sort.ts
+++ b/src/custom-sort/custom-sort.ts
@@ -49,20 +49,6 @@ export const CollatorCompare = new Intl.Collator(undefined, {
 	numeric: true,
 }).compare;
 
-export const CollatorCompareUpperFirst = new Intl.Collator(undefined, {
-	usage: "sort",
-	sensitivity: "base",
-	numeric: true,
-	caseFirst: "upper"
-}).compare;
-
-export const CollatorCompareLowerFirst = new Intl.Collator(undefined, {
-	usage: "sort",
-	sensitivity: "base",
-	numeric: true,
-	caseFirst: "lower"
-}).compare;
-
 export const CollatorTrueAlphabeticalCompare = new Intl.Collator(undefined, {
 	usage: "sort",
 	sensitivity: "base",
@@ -193,16 +179,12 @@ const folderGoesFirstWhenSameBasenameAsFolder = (stringCompareResult: number, a:
 
 const Sorters: { [key in CustomSortOrder]: SorterFn } = {
 	[CustomSortOrder.alphabetical]: (a: FIFS, b: FIFS) => CollatorCompare(a.sortString, b.sortString),
-	[CustomSortOrder.alphabeticalLowerFirst]: (a: FIFS, b: FIFS) => CollatorCompareLowerFirst(a.sortString, b.sortString),
-	[CustomSortOrder.alphabeticalUpperFirst]: (a: FIFS, b: FIFS) => CollatorCompareUpperFirst(a.sortString, b.sortString),
 	[CustomSortOrder.alphabeticalWithFilesPreferred]: (a: FIFS, b: FIFS) => fileGoesFirstWhenSameBasenameAsFolder(CollatorCompare(a.sortString, b.sortString),a,b),
 	[CustomSortOrder.alphabeticalWithFoldersPreferred]: (a: FIFS, b: FIFS) => fileGoesFirstWhenSameBasenameAsFolder(CollatorCompare(a.sortString, b.sortString),a,b),
 	[CustomSortOrder.alphabeticalWithFileExt]: (a: FIFS, b: FIFS) => CollatorCompare(a.sortStringWithExt, b.sortStringWithExt),
 	[CustomSortOrder.trueAlphabetical]: (a: FIFS, b: FIFS) => CollatorTrueAlphabeticalCompare(a.sortString, b.sortString),
 	[CustomSortOrder.trueAlphabeticalWithFileExt]: (a: FIFS, b: FIFS) => CollatorTrueAlphabeticalCompare(a.sortStringWithExt, b.sortStringWithExt),
 	[CustomSortOrder.alphabeticalReverse]: (a: FIFS, b: FIFS) => CollatorCompare(b.sortString, a.sortString),
-	[CustomSortOrder.alphabeticalLowerFirstReverse]: (a: FIFS, b: FIFS) => CollatorCompareLowerFirst(b.sortString, a.sortString),
-	[CustomSortOrder.alphabeticalUpperFirstReverse]: (a: FIFS, b: FIFS) => CollatorCompareUpperFirst(b.sortString, a.sortString),
 	[CustomSortOrder.alphabeticalReverseWithFileExt]: (a: FIFS, b: FIFS) => CollatorCompare(b.sortStringWithExt, a.sortStringWithExt),
 	[CustomSortOrder.trueAlphabeticalReverse]: (a: FIFS, b: FIFS) => CollatorTrueAlphabeticalCompare(b.sortString, a.sortString),
 	[CustomSortOrder.trueAlphabeticalReverseWithFileExt]: (a: FIFS, b: FIFS) => CollatorTrueAlphabeticalCompare(b.sortStringWithExt, a.sortStringWithExt),
diff --git a/src/custom-sort/sorting-spec-processor.spec.ts b/src/custom-sort/sorting-spec-processor.spec.ts
index 7ffb127..5b9201a 100644
--- a/src/custom-sort/sorting-spec-processor.spec.ts
+++ b/src/custom-sort/sorting-spec-processor.spec.ts
@@ -711,15 +711,8 @@ describe('SortingSpecProcessor', () => {
 	})
 })
 
+
 const txtInputExoticExperimentalSortAttr: string = `
-target-folder: upper first
-< aaa-z
-target-folder: upper first Rev
-> aaa-z
-target-folder: lower first
-< a-zzz
-target-folder: lower first Rev
-> a-zzz
 target-folder: VS Code unicode lexicographic
 < vsc-unicode
 target-folder: VS Code unicode lexicographic reverse
@@ -727,38 +720,6 @@ target-folder: VS Code unicode lexicographic reverse
 `
 
 const expectedSortSpecForExoticExperimentalSorting: { [key: string]: CustomSortSpec } = {
-	"upper first": {
-		defaultOrder: CustomSortOrder.alphabeticalUpperFirst,
-		groups: [{
-			type: CustomSortGroupType.Outsiders
-		}],
-		outsidersGroupIdx: 0,
-		targetFoldersPaths: ['upper first']
-	},
-	"upper first Rev": {
-		defaultOrder: CustomSortOrder.alphabeticalUpperFirstReverse,
-		groups: [{
-			type: CustomSortGroupType.Outsiders
-		}],
-		outsidersGroupIdx: 0,
-		targetFoldersPaths: ['upper first Rev']
-	},
-	"lower first": {
-		defaultOrder: CustomSortOrder.alphabeticalLowerFirst,
-		groups: [{
-			type: CustomSortGroupType.Outsiders
-		}],
-		outsidersGroupIdx: 0,
-		targetFoldersPaths: ['lower first']
-	},
-	"lower first Rev": {
-		defaultOrder: CustomSortOrder.alphabeticalLowerFirstReverse,
-		groups: [{
-			type: CustomSortGroupType.Outsiders
-		}],
-		outsidersGroupIdx: 0,
-		targetFoldersPaths: ['lower first Rev']
-	},
 	"VS Code unicode lexicographic": {
 		defaultOrder: CustomSortOrder.vscUnicode,
 		groups: [{
diff --git a/src/custom-sort/sorting-spec-processor.ts b/src/custom-sort/sorting-spec-processor.ts
index 4fc8e79..8caed88 100644
--- a/src/custom-sort/sorting-spec-processor.ts
+++ b/src/custom-sort/sorting-spec-processor.ts
@@ -116,10 +116,8 @@ const MAX_SORT_LEVEL: number = 1
 
 // remember about .toLowerCase() before comparison!
 const OrderLiterals: { [key: string]: CustomSortOrderAscDescPair } = {
-	'a-zzz': {asc: CustomSortOrder.alphabeticalLowerFirst, desc: CustomSortOrder.alphabeticalLowerFirstReverse},
 	'a-z.': {asc: CustomSortOrder.alphabeticalWithFileExt, desc: CustomSortOrder.alphabeticalReverseWithFileExt},
 	'a-z': {asc: CustomSortOrder.alphabetical, desc: CustomSortOrder.alphabeticalReverse},
-	'aaa-z': {asc: CustomSortOrder.alphabeticalUpperFirst, desc: CustomSortOrder.alphabeticalUpperFirstReverse},
 	'true a-z.': {asc: CustomSortOrder.trueAlphabeticalWithFileExt, desc: CustomSortOrder.trueAlphabeticalReverseWithFileExt},
 	'true a-z': {asc: CustomSortOrder.trueAlphabetical, desc: CustomSortOrder.trueAlphabeticalReverse},
 	'created': {asc: CustomSortOrder.byCreatedTime, desc: CustomSortOrder.byCreatedTimeReverse},