Pros: The single best replacement to LuX I and Lux III emitters that aren't already soldered to a star. For the same watts you get double output or for the same output you use half the watts. The choice is clear.

Cons: Gummy dome. Just be careful. Polarity - just be careful and test the emitter for a split second before installing. Fragile until it's installed. Comes packaged in such a way as to subject it to possible damage during shipping. Could be packaged better.

Other Thoughts: The emitter puts light out just slightly lower in height than a standard LUX so you may need to adjust your reflector or shim up the SSCP4.

Bottomline: Get it. There isn't really a brighter single die luxIII replacement emitter, only warmer ones.

Pros: + Same footprint as Luxeon package
+ Suitable for 4.5 V (3x LR1) direct drive with proper heatsink
+ Significant more light output
+ Cheap and relatively easy upgrade for LED Lenser torches

Cons: - Soft lens dome is more fragile compared to Luxeon
- Unlike the Luxeon package the SSC metal base is not electrically isolated but connects with the anode(+)!

Other Thoughts: First of all I wish to thank DX for a quick service even during Christmas time. Keep up the good work!
Next I would like to wallop the other reviewers who failed to notice the rather big issue with SSC's metal base which is supposed to connect with a heat sink: Most good torches have the heatsink connected to their metal body which is commonly negative (-). That's OK with Luxeon but causes a short using the SSC, who for only Kimchi-eaters-know-why connected it with the anode side (+).
Frustrating, but fixable by adding an insulation pad between with heat conducting paste on both sides. However the excellent thermal conductivity in the LED Lenser design is now degraded. We'll see how long the SSC P4 holds in direct-drive.

Bottomline: The SSC P4 is a good replacement for Luxeon, but be sure to electrically isolate the heatsink.

Pros: Its hard to go wrong with the P4s as they make great upgrades to Luxeon LED lights. The form factor of the P4 makes upgrading easy.

Cons: Some soldering experience recommended to solder bare emitter, but its fairly easy with a good iron.

Other Thoughts:

Bottomline: If you have an older light (I upgraded a Niterider Minewt) that uses a Luxeon LED, this is the perfect replacement. Its just about .2mm shorter, and the pins line up perfectly. Remove old LED, install this, and you have an instant huge upgrade.
Make sure you check with a multimeter, or mark which is + and -ve before you remove old emitter.
Also if your old light has uses a Luxeon star, I'd suggest getting the P4 mounted on a star, which would be a bit easier to work with anyways.

Pros: Prices lower than other suppliers.
Very powerfull led. Directly connected to Li-ion battery makes a perfect flashlight. More powerfull then other brands that I bought earlier.
Very interresting when paying with euro's

Cons: Not really a con. but more a warning. Do supply sufficient cooling when powered by i.e. 18650 Li-ion battery directly. Wonder if the silicone dome will stay clear after a longer period of use.

Other Thoughts: Also available with star heatsink for easy modifying of standard flashlights. Very good for making a powerfull flaslight combined with the bare barrel (SKU 15159)

Bottomline: No better ones found so far for making flashlights.