diff --git a/go/mflags/limiter.go b/go/mflags/limiter.go
new file mode 100644
index 0000000..c085b52
--- /dev/null
+++ b/go/mflags/limiter.go
@@ -0,0 +1,40 @@
+// Package mflags implements custom flags for use in monogon projects.
+// It provides them to be used like normal flag.$Var and registers the
+// required flag functions.
+package mflags
+
+import (
+	"flag"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"golang.org/x/time/rate"
+)
+
+// Limiter configures a *rate.Limiter as a flag.
+func Limiter(l **rate.Limiter, name, defval, help string) {
+	syntax := "'duration,count' eg. '2m,10' for a 10-sized bucket refilled at one token every 2 minutes"
+	help = help + fmt.Sprintf(" (default: %q, syntax: %s)", defval, syntax)
+	flag.Func(name, help, func(val string) error {
+		if val == "" {
+			val = defval
+		}
+		parts := strings.Split(val, ",")
+		if len(parts) != 2 {
+			return fmt.Errorf("invalid syntax, want: %s", syntax)
+		}
+		duration, err := time.ParseDuration(parts[0])
+		if err != nil {
+			return fmt.Errorf("invalid duration: %w", err)
+		}
+		refill, err := strconv.ParseUint(parts[1], 10, 31)
+		if err != nil {
+			return fmt.Errorf("invalid refill rate: %w", err)
+		}
+		*l = rate.NewLimiter(rate.Every(duration), int(refill))
+		return nil
+	})
+	flag.Set(name, defval)
+}