THE MFJ-310S is similar to the MFJ-310, except the MFJ-310S has a SMA connector.;By mounting your handheld's antenna outside your car, your antenna radiates freely and greatly extends your range.;With MFJ's Window Mount Clip you can mount your handheld antenna outside in seconds on the top edge of any window in your car. It's firmly held in place when you roll up your window.;The MFJ-310S works with any 2 meter, 220MHz, dual band or any other handheld that uses a SMA antenna connector.