The stock TIR doesn’t have a 5050 hole–a 5050 footprint has a diagonal (thus diameter) of around 7mm, so 5.70 as pictured would not do. It looks like the optic is not enveloping the footprint but sitting on top of it, so what matters is not footprint size but dome size (or size of light-emitting area). Thus if you use a 7070 domeless emitter (such as the XHP70.3HI) the stock optic should suffice–according to this test one can calculate the diagonal of the XHP70.3HI light-emitting surface to be around 5.4mm, which is less than (thus compatible with) the 5.70 as pictured.
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