I also have the IR with the composite body. I'm pretty sure the model number is 2141 for the 3/4" and 2131 for the 1/2". My 3/4" will outdo a couple of older 1" impacts that I used to borrow. It's also not much heavier than the IR 1/2" steel body impact that I have. Put a good 1/2" line to it to feed it and you're good to go on most anything I have around here. I bought mine on ebay - can't remember exact price, but it was new and the cheapest I could find.

HTH,

Mike