ES-sigma enable user to enjoy the speaker-like sound of this legendary model without having to be troubled by the availability, high price, service issues and driver deterioration problem which are common on the original sigma.  ES-sigma uses a pair of 404 driver with has a higher resolution, imaging and transparency than the original sigma. 
 
ES lab offers 3 solution to provide modding services:
 
1) We offer stock for sale
 
2) You can ship your lambda model electrostatic headphone to us for modding
 
3)headphone enclosure can be sold separately so that you can carry out the modding your self