diff --git a/docs/api-reference.md b/docs/api-reference.md
index 81c0be1f7..8c083d514 100644
--- a/docs/api-reference.md
+++ b/docs/api-reference.md
@@ -95,11 +95,13 @@ Response:
 
 In order to send protobuf binaries in the request and response, set `Content-Type` and `Accept` headers to: `application/x-protobuf`.
 
-The response doesn't include column attributes by default. To return them, set `columnAttrs` query argument to `true`.
+The response doesn't include column attributes by default. To return them, set the `columnAttrs` query argument to `true`.
+
+The query is executed for all [slices](../data-model#slice) by default. To use specified slices only, set the `slices` query argument to a comma-separated list of slice indices.
 
 Request:
 ```
-curl localhost:10101/index/user/query?columnAttrs=true \
+curl "localhost:10101/index/user/query?columnAttrs=true&slices=0,1" \
      -X POST \
      -d 'Bitmap(frame="language", id=5)'
 ```
diff --git a/docs/data-model.md b/docs/data-model.md
index b4b98de9a..f8987f87b 100644
--- a/docs/data-model.md
+++ b/docs/data-model.md
@@ -54,7 +54,7 @@ Attributes are arbitrary key/value pairs that can be associated to both rows or
 
 ### Slice
 
-Indexes are sharded into groups of columns called Slices - each Slice contains a fixed number of columns which is the SliceWidth.
+Indexes are sharded into groups of columns called Slices - each Slice contains a fixed number of columns which is the SliceWidth. SliceWidth is a non-configurable constant set to 2<sup>20</sup>.
 
 Columns are sharded on a preset width, and each shard is referred to as a Slice.  Slices are operated on in parallel, and they are evenly distributed across a cluster via a consistent hash algorithm.