Jamieson, Fausset and Brown on Exodus 25:5

5. badgers' skins--The badger was an unclean animal, and is not a native of the East--rather some kind of fish, of the leather of which sandals are made in the East. [See on Ex 39:34 and Eze 16:10.]

shittim wood--or Shittah (Is 41:19), the acacia, a shrub which grows plentifully in the deserts of Arabia, yielding a light, strong, and beautiful wood, in long planks.