Don: Thanks, I found this on the TradeSlang Site.
Expansion Deflection couplings (joints) are fittings that allow for 3/4" movement in any direction between two pieces of Rigid, IMC or PVC conduit.
The deflection term comes from its ability to bend up to 30 degrees. They are typically used when the conduit has to withstand vibration from machinery or vehicles.
Made by Crouse-Hinds, OZ Gedney and others, they come in sizes ranging from 1/2" to 6".
[This message has been edited by Joe Tedesco (edited 09-02-2002).]