Product composition: there are 4 control knobs and and 12 pieces adapters, adapters includes 4 long small hole adapters, 4 short small hole adapters and 4 short big hole adapters, works with many brand stove, range and oven, suitable for RVs, campers, camping appliances, etc. But not all brands and models are suitable, not suit for heaters or barbecues such as BBQAdapter Size: there are 12 pieces adapters, 4 long and 8 short; The inner diameter of the long small hole adapter is the same as the inner diameter of the short small hole adapter, they has long inner diameter of 0.22"/5.5 mm and short inner diameter of 0.18"/4.5 mm; Short Large Bore Adapter has a long inner diameter of 0.3"/7.5 mm and a short inner diameter of 0.26"/6.5 mm;Convenient for your daily usage; Please check carefully whether the dimensions in Figure 3 matchKnob Size: comes with 4 pieces same size control knobs; And the control knob's outer diameter measures approx. 1.57 "/ 40 mm; The inner diameter of knob approx. 0.43"/ 11 mm; The control knob is connected to the stove switch through the adapter, so the control knob is connected to one end of the adapter，Please check carefully with Figure 4Easy to use: Before purchasing, measure the size of your stove switch shaft to make sure it is slightly smaller than our adapter (refer to Figure 3 for dimensions); after delivery, connect the adapter and control knob first, then insert the other end of the adapter into the switch shaft. Note that the concave point is aligned with the starting point (refer to Figure 6 for steps)Durable materail: our control knobs made of quality material ABS plastic, these knobs and adapters have been well inspected and test by manufacturer; Please note: before buying, please confirm whether the plastic knob is what you need