disco or non-disco axle shafts

i need some new axle shafts for my dana 30 up front in a 90 cherokee and i am confused i don't know the differenece between disco shafts and non disco shafts if someone knows please explain this tto me thanks

Some XJs had vacuum disconnect (disco) on the passenger side. These have 2 piece inner axleshafts and a vacuum shift motor on the rear of the axletube. The others -ones with a NP 242 "full-time 4x4" transfer case had a one-piece (non-disco) axleshaft and a 'smooth' axle tube.

The Disco style can be converted to non disco with a special seal and that 1 piece shaft.

Later model XJs all had non-disco's and the ones with ABS got the larger Spicer 5-297X (760) U-joint size. If you have & keep the disco feature, an outer shaft from a YJ Wrangler with ABS will have the bigger UJ. The smaller UJ size is 5-260x.

HTH