Shaft sizing on the spring handles vary.  Some work may be required to get them to fit snuggly.  You can reduce the size on a loose fitting handle by clamping the last turn of the spring and squeezing it in a vice or with slip joint pliers.  This needs to be done off the metal rod/handle.  If the fit is tight you can twist (screw) the handle on.  Some customers have slightly rounded or tapered the handle shaft on their stove by grinding or filing the end and then screw the spring handle on.
 
Measurement: 4" Long - 5/16" to 1/2" Shank

Part # RH-DB