diff --git a/ENV.md b/ENV.md
index 7690aad..f60bfd0 100644
--- a/ENV.md
+++ b/ENV.md
@@ -1,5 +1,7 @@
 # Test rig
 
+Using `mongo:latest` image, tested on "MONGO_VERSION=4.0.1".
+
 # Docker for Windows 
 
 | Key            | Value                        |
@@ -11,15 +13,3 @@
 | Built          | Wed Jul 18 19:13:46 2018     |
 | OS/Arch        | windows/amd64                |
 | Experimental   | false                        |
-
-# Linux
-
-| Key            | Value              |
-|----------------|--------------------|
-| Version        | 1.12.6             |
-| API version    | 1.24               |
-| Go version     | go1.6.4            |
-| OS type        | linux              |
-| OS             | Ubuntu 16.04.1 LTS |
-| Architecture   | amd64              |
-| Kernel version | 4.4.0-57-generic   |
\ No newline at end of file
diff --git a/docker-compose.1.yml b/docker-compose.1.yml
index ac99e70..d81cd5b 100644
--- a/docker-compose.1.yml
+++ b/docker-compose.1.yml
@@ -2,7 +2,7 @@ version: '3'
 services:
     mongo-1-2:
         container_name: "mongo-1-2"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30012:27017"
         command: mongod --replSet rs1 --shardsvr --port 27017  --oplogSize 16 --noprealloc --smallfiles
@@ -10,7 +10,7 @@ services:
 
     mongo-1-3:
         container_name: "mongo-1-3"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30013:27017"
         command: mongod --replSet rs1 --shardsvr --port 27017  --oplogSize 16 --noprealloc --smallfiles
@@ -18,7 +18,7 @@ services:
 
     mongo-1-1:
         container_name: "mongo-1-1"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30011:27017"
         command: mongod --replSet rs1 --shardsvr --port 27017  --oplogSize 16 --noprealloc --smallfiles
@@ -29,7 +29,7 @@ services:
 
     mongo-rs1-setup:
         container_name: "mongo-rs1-setup"
-        image: mongo
+        image: mongo:4.0.1
         depends_on:
             - "mongo-1-1"
             - "mongo-1-2"
diff --git a/docker-compose.2.yml b/docker-compose.2.yml
index d490071..47f162e 100644
--- a/docker-compose.2.yml
+++ b/docker-compose.2.yml
@@ -2,7 +2,7 @@ version: '3'
 services:
     mongo-2-2:
         container_name: "mongo-2-2"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30022:27017"
         command: mongod --replSet rs2 --shardsvr --port 27017  --oplogSize 16 --noprealloc --smallfiles
@@ -10,7 +10,7 @@ services:
 
     mongo-2-3:
         container_name: "mongo-2-3"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30023:27017"
         command: mongod --replSet rs2 --shardsvr --port 27017  --oplogSize 16 --noprealloc --smallfiles
@@ -18,7 +18,7 @@ services:
 
     mongo-2-1:
         container_name: "mongo-2-1"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30021:27017"
         command: mongod --replSet rs2 --shardsvr --port 27017  --oplogSize 16 --noprealloc --smallfiles
@@ -29,7 +29,7 @@ services:
 
     mongo-rs2-setup:
         container_name: "mongo-rs2-setup"
-        image: mongo
+        image: mongo:4.0.1
         depends_on:
             - "mongo-2-1"
             - "mongo-2-2"
diff --git a/docker-compose.cnf.yml b/docker-compose.cnf.yml
index 87432e8..b4f57ee 100644
--- a/docker-compose.cnf.yml
+++ b/docker-compose.cnf.yml
@@ -2,7 +2,7 @@ version: '3'
 services:
     mongo-cnf-2:
         container_name: "mongo-cnf-2"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30102:27017"
         command: mongod --replSet cnf-serv --configsvr --port 27017 --oplogSize 16 --noprealloc --smallfiles
@@ -10,7 +10,7 @@ services:
 
     mongo-cnf-3:
         container_name: "mongo-cnf-3"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30103:27017"
         command: mongod --replSet cnf-serv --configsvr --port 27017 --oplogSize 16 --noprealloc --smallfiles
@@ -18,7 +18,7 @@ services:
 
     mongo-cnf-1:
         container_name: "mongo-cnf-1"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30101:27017"
         command: mongod --replSet cnf-serv --configsvr --port 27017 --oplogSize 16 --noprealloc --smallfiles
@@ -29,7 +29,7 @@ services:
 
     mongo-cnf-setup:
         container_name: "mongo-cnf-setup"
-        image: mongo
+        image: mongo:4.0.1
         depends_on:
             - "mongo-cnf-1"
             - "mongo-cnf-2"
diff --git a/docker-compose.shard.yml b/docker-compose.shard.yml
index 0226b3a..fd5283f 100644
--- a/docker-compose.shard.yml
+++ b/docker-compose.shard.yml
@@ -2,7 +2,7 @@ version: '3'
 services:
     mongo-router:
         container_name: "mongo-router"
-        image: mongo
+        image: mongo:4.0.1
         ports:
             - "30001:27017"
         depends_on:
@@ -24,7 +24,7 @@ services:
 
     mongo-shard-setup:
         container_name: "mongo-shard-setup"
-        image: mongo
+        image: mongo:4.0.1
         depends_on:
             - "mongo-router"
         links: