Use this to convert your 50LR or 66LR into our 50LRX or 66LRX light. This will give you a faster focus from flood beam to spot beam as it will only take about 3/4 turn of the head to go from full flood beam to full spot beam as our 50LR and 66LR take about 1 3/4 turns to do the same. Also, if your light has any play in the head, this will eliminate the play in the head. You can also use this to make another light if you have any extra 38LRX, 50LR, 50LRX, 66LR and 66LRX heads, you will also need a extra LED module and tail cap. All our previous LED modules and tail caps for our 30LR, 38LRX, 50LR, 50LRX, 66LR and 66LRX lights will work with this Tube and bottom of the head.