diff --git a/main.go b/main.go
index e13da99..f1c2cc3 100644
--- a/main.go
+++ b/main.go
@@ -635,7 +635,7 @@ func main() {
 		streams  = flag.Int("streams", 7, "independent streams per direction, capped by rx rings; each gets its own ethertype, steered by a flow rule to its own rx queue")
 		batch    = flag.Int("batch", 64, "frames per sendmmsg/recvmmsg call")
 
-		nsPerM = flag.Float64("ns-per-m", 5.2, "mean of both directions, per metre of cable")
+		nsPerM = flag.Float64("ns-per-m", 4.85, "mean of both directions, per metre of cable")
 	)
 	flag.Parse()