Hello there, I think I have helped you out before on your PPL questions in the past.
Haha I know exactly the ones you mean! They wouldn't be green in colour by any chance would they?
To be honest Sennheiser are a much respected brand, but I think they are more renowned for use in quiet flight deck environments (737s, 320s etc.) not in a noisy GA
aircraft. Most PPL's stick with the David Clark head sets, they are cheaper. However the headset you mentioned can be used in GA
aircraft it seems from its synopsis.
"Sennheiser's HMEC 25-KA active noise headset is designed for use in a jet flight-deck environment, providing up to 26dB active noise cancelling with 11dB of passive. This light headset is ideal for small aircraft use also. Weighing in at only 170g, and featuring an electret noise cancelling microphone, fold-back earpiece for single-ear use, and a split headband."
It seems from that it can be used in a GA
Give us a shout if you need any more help.