diff --git a/src/core/CCArray.ml b/src/core/CCArray.ml
index a075efa9..3f4b0ec4 100644
--- a/src/core/CCArray.ml
+++ b/src/core/CCArray.ml
@@ -170,7 +170,7 @@ let sort_indices cmp a =
 *)
 
 (*$Q
-  Q.(array printable_string) (fun a -> \
+  Q.(array_of_size Gen.(0 -- 30) printable_string) (fun a -> \
     let b = sort_indices String.compare a in \
     sorted String.compare a = Array.map (Array.get a) b)
 *)
@@ -485,7 +485,7 @@ let swap a i j =
 *)
 
 (*$QR
-  Q.(array small_int) (fun a ->
+  Q.(array_of_size Gen.(0 -- 100) small_int) (fun a ->
     let b = Array.copy a in
     for i = 0 to Array.length a-1 do
       for j = i+1 to Array.length a-1 do
diff --git a/src/core/CCParse.ml b/src/core/CCParse.ml
index 2570a512..50dd98ca 100644
--- a/src/core/CCParse.ml
+++ b/src/core/CCParse.ml
@@ -68,8 +68,7 @@
 
     assert_equal ~printer:Q.Print.(list int) l l'
   in
-  test 100_000;
-  test 400_000;
+  test 300_000;
 
 *)
 
diff --git a/src/core/CCString.ml b/src/core/CCString.ml
index c127e097..0c813d5b 100644
--- a/src/core/CCString.ml
+++ b/src/core/CCString.ml
@@ -918,7 +918,7 @@ let unlines_gen g =
 *)
 
 (*$Q
-  Q.(list string) (fun l -> \
+  Q.(small_list small_string) (fun l -> \
     let l = unlines l |> lines in \
     l = (unlines l |> lines))
 *)
diff --git a/src/core/CCUtf8_string.ml b/src/core/CCUtf8_string.ml
index 60ccf1b5..11eca5dd 100644
--- a/src/core/CCUtf8_string.ml
+++ b/src/core/CCUtf8_string.ml
@@ -263,13 +263,13 @@ let of_string s = if is_valid s then Some s else None
 *)
 
 (*$QR
-  Q.string (fun s ->
+  Q.small_string (fun s ->
     Q.assume (CCString.for_all (fun c -> Char.code c < 128) s);
     is_valid s)
 *)
 
 (*$QR & ~long_factor:10
-  Q.string (fun s ->
+  Q.small_string (fun s ->
     Q.assume (CCString.for_all (fun c -> Char.code c < 128) s);
     s = (of_string_exn s |> to_seq |> of_seq |> to_string)
   )
@@ -312,8 +312,8 @@ let of_string s = if is_valid s then Some s else None
 
 (* compare with uutf *)
 
-(*$QR & ~long_factor:40 ~count:100_000
-  Q.string (fun s ->
+(*$QR & ~long_factor:40 ~count:50_000
+  Q.small_string (fun s ->
     let v1 = is_valid s in
     let v2 = uutf_is_valid s in
     if v1=v2 then true
@@ -321,8 +321,8 @@ let of_string s = if is_valid s then Some s else None
   )
 *)
 
-(*$QR & ~long_factor:40 ~count:100_000
-  Q.string (fun s ->
+(*$QR & ~long_factor:40 ~count:50_000
+  Q.small_string (fun s ->
     Q.assume (is_valid s && uutf_is_valid s);
     let pp s = Q.Print.(list pp_uchar) s in
     let l_uutf = uutf_to_seq s |> Sequence.to_list in
diff --git a/src/data/CCRingBuffer.ml b/src/data/CCRingBuffer.ml
index 7c2e88b7..dc5cc173 100644
--- a/src/data/CCRingBuffer.ml
+++ b/src/data/CCRingBuffer.ml
@@ -744,7 +744,7 @@ module Make(Elt:sig
     ~print:str_of_op
     gen_op
 
-  let arb_ops = Q.list arb_op
+  let arb_ops = Q.list_of_size Q.Gen.(0 -- 20) arb_op
 
   module L_impl = struct
   type t = {