Many decades ago, I bought 1 yard of vinyl
surgical tubing at a local hardware store,
with the proper OD (outer diameter) and
ID (inner hole diameter).
I had measured the bumper tubing from
a Hohner #270, before the purchase. The
tubing measurements have worked on all
of my Hohner slide harps and other brands.
I still have most of the 1 yard of tubing.
Being of Irish descent, I've always loved
tubers (potatoes).
Best Regards, Stay Healthy
JB