Anderson Double Hung window sash replacement

I have several anderson double hung windows which require new sash. The windows are appox. 30 plus years old. the part number reads BL10 10#314 plus either a R or 8. Since it is from the right side facing out from the inside I think it might be indication a right side sash. Could you direct me to the current unit replacement and is there any difference from a right side for left side? I will need both for each window. The unit measures 6.75 x 3 inches.

Each window panel of the Double hung measure 35W x 32H.