The Premium Bellows
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This yields an unproductive stroke, requiring more pumping. The metal hinge ensures an identical stroke with every pump, ensuring that the 2 cheeks remain parallel to each other in operation. This means that virtually all the air is exhausted by the stroke, which means less pumping. Considering the amount of pumping required for a typical session or performance, this can be quite significant.
So why pay more for the Premium bellows?
The pads, back and front, are upholstered to the wood cheeks of the bellows and retained with inlaid stainless steel trim. The advantage here, apart from the obvious aesthetic, is that the pads are always there, in the same spot, so you will not only not lose them, but, more importantly, they locate themselves in exactly the same spot every time on your elbow and hip to which you have become accustomed. No slippage and re-adjusting.
A strong but attractive looking stainless steel hinge ensures strength and durability over many years of use. The main advantage here is significant, if not immediately apparent. With the floppier leather hinge, the cheeks, or timber paddles of the bellows, tend to close unevenly under pressure leaving up to 30% of the air inside the bellows, when only the tops of the cheeks meet.