diff --git a/dive.h b/dive.h
index c6c545dcc..2d03ee7cd 100644
--- a/dive.h
+++ b/dive.h
@@ -75,6 +75,7 @@ typedef struct {
 typedef struct {
 	volume_t size;
 	pressure_t workingpressure;
+	const char *description;	/* "LP85", "AL72", "AL80", "HP100+" or whatever */
 } cylinder_type_t;
 
 typedef struct {