Drone Valves by McCallum Bagpipes are designed to assist pipers in achieving consistent and steady strike-ins and cut-offs. They are simply fitted into the bottom of each drone stock inside the bag. They can be fitted by adding some hemp until they form a secure press fit.
Adjustments can be made by very slightly shortening or lengthening the elastic which is holding the valve flap in place. The valves can be easily set up by blowing through each valve into the drone.
If there is a fluttering sound coming from the valve then it is set too tight and if the valve flap is set too loose then the valve will not perform effectively on cut-offs.
The McCallums drone valves are suitable for most bag set ups with access to the inside of the bag.