Gasket and Seal Kit mainly contain gaskets and seals.

Bearing, Gasket and Seal kits mainly contain gaskets, seals, bearings and small parts.

Synchro, Bearing, Gasket and Seal kits mainly contain all of the above plus synchro rings, synchro repair kit and other high wear components deemed necessary.

Your application may or may not contain some of the parts listed depending or your transmission model.