diff --git a/categories/img/mp/pipe.mp b/categories/img/mp/pipe.mp
index be63e87..49e75bd 100644
--- a/categories/img/mp/pipe.mp
+++ b/categories/img/mp/pipe.mp
@@ -1,12 +1,25 @@
 
+vardef inmouthsize(expr pos,size) =
+    fullcircle xscaled 0.6 scaled size shifted pos
+enddef;
+vardef outmouthsize(expr pos,size) =
+    (subpath (0,4) of fullcircle rotated -90) xscaled 0.6 scaled size shifted pos
+enddef;
+vardef hiddenoutmouthsize(expr pos,size) =
+    (subpath (4,8) of fullcircle rotated -90) xscaled 0.6 scaled size shifted pos
+enddef;
 vardef inmouth(expr pos) =
-    fullcircle xscaled 0.6 scaled 2u shifted pos
+    inmouthsize(pos,2u)
 enddef;
 vardef outmouth(expr pos) =
-    (subpath (0,4) of fullcircle rotated -90) xscaled 0.6 scaled 2u shifted pos
+    outmouthsize(pos,2u)
 enddef;
 vardef hiddenoutmouth(expr pos) =
-    (subpath (4,8) of fullcircle rotated -90) xscaled 0.6 scaled 2u shifted pos
+    hiddenoutmouthsize(pos,2u)
+enddef;
+def drawoutmouth(expr pos) =
+    draw outmouth(pos);
+    draw hiddenoutmouth(pos) dashed evely;
 enddef;
 
 def drawtube(expr pos) =
@@ -15,10 +28,8 @@ def drawtube(expr pos) =
     pair midin,midout;
     midin := pos;
     midout := pos shifted (gu,0);
-    draw outmouth(midin);
-    draw hiddenoutmouth(midin) dashed evenly;
-    draw outmouth(midout);
-    draw hiddenoutmouth(midout) dashed evenly;
+    drawoutmouth(midin);
+    drawoutmouth(midout);
 
     save topin,topout,botin,botout;
     pair topin,topout,botin,botout;
@@ -68,16 +79,53 @@ def drawtwotubeslabel(expr ptop,pbot,pout,l) =
     endgroup;
 enddef;
 def drawbegintube (expr pos) =
-    draw (subpath (4,8) of fullcircle rotated -90) scaled 2u shifted pos;
+    draw (subpath (4,8) of fullcircle rotated -90) scaled 2u shifted pos shifted (-2u,0);
+    draw (pos shifted (-2u,u)){right}..{right}(pos shifted (0,u));
+    draw (pos shifted (-2u,-u)){right}..{right}(pos shifted (0,-u));
     draw outmouth(pos);
     draw hiddenoutmouth(pos) dashed evenly;
 enddef;
 
 def drawbegintubelabel(expr pos,l) =
     drawbegintube(pos);
-    label(l,pos);
+    label(l,pos shifted (-1.5u,0));
 enddef;
 
-drawbegintubelabel((0,gu),btex $37$ etex);
-drawtubelabel(origin,btex $+$ etex);
-drawtwotubeslabel((0,-gu),(0,-2gu),(gu,-1.5gu),btex $+$ etex);
+def drawtube(expr pos) =
+    begingroup;
+    save midin,midout;
+    pair midin,midout;
+    midin := pos;
+    midout := pos shifted (gu,0);
+    draw outmouth(midin);
+    draw hiddenoutmouth(midin) dashed evenly;
+    draw outmouth(midout);
+    draw hiddenoutmouth(midout) dashed evenly;
+
+    save topin,topout,botin,botout;
+    pair topin,topout,botin,botout;
+    topin=pos shifted (0,u);
+    topout=topin shifted (gu,0);
+    botin=pos shifted (0,-u);
+    botout=botin shifted (gu,0);
+    draw topin -- topout;
+    draw botin -- botout;
+    endgroup;
+enddef;
+def drawtubelabel(expr pos,l) =
+    drawtube(pos);
+    label(l,pos shifted (.5gu,0));
+enddef;
+
+pair pos;
+pos:=(gu,gu);
+drawbegintubelabel(pos shifted (-gu,.5gu),btex $37$ etex);
+drawbegintubelabel(pos shifted (-gu,-.5gu),btex $\mathtt{"foo"}$ etex);
+drawtwotubeslabel(pos shifted (0,.5gu), pos shifted (0,-.5gu), pos shifted (gu,0),btex $+$ etex);
+
+z0=origin;
+drawbegintubelabel(z0,btex $37$ etex);
+drawtwotubeslabel(z0, z0 shifted (0,-gu), z0 shifted (gu,-0.5gu),btex $+$ etex);
+
+drawtubelabel(z0 shifted (2gu,-.5gu),btex $37+$ etex);
+