I'm not 100% sure what 6+7" means?
The microfiber pads are available in 3 different sizes:
The 170mm pads with a 150mm mounting face for the LHR 21ES.
The 150mm pads with a 125mm mounting ace for the LHR 15ES/Duetto
The 100mm pads with a 80mm mounting face for the LHR 75E Mini and LHR 75 air driven polisher.
The one with the straight cut is the 170mm, the one with the beveled cut is the 150mm. There is a slight difference between the actually polishing face of the 170mm and 150mm pads, it isn't 20mm. I believe both measure close to 150mm (about 6 inches), and the name difference is just to clarify the models.
In addition to the difference in mounting faces, both pads weigh different. The 170's are a closer match to the 21's counterbalance and the 150's are a closer match to the 15's counterbalance. However, neither is perfect and if you hold the machines is free air (off the paint) you will feel a slight buzz with the microfiber that you will not feel with the foam pads. If you plan on using the microfibers a lot we do have a different backing plate that will optimize the weight and dynamic balance should you desire.
Does this help?
Ray..bumping this for you.
Will you be offering the MF backing plate eventually?