This a new genuine authentic H. Miller Mirra replacement seat pan will only fit Mirra 2 Chair model numbers requiring a FLEXED front seat indicated by an "A" in the 7th character space of the model number (i.e. MRF12xAm or MRF23aAm, etc.). Beginning Model numbers include ; MRF11, MRF12, MRF13, MRF21, MRF22, MRF23, MRF31, MRF32 & MRF33 This Mirra 1 chair seat pan has an Airweave* seat suspension material that is lightweight and breathable and evenly distributes the user's weight over the seat of the chair. If you have any questions prior to ordering, we will be happy to assist.