Yes, T400 refer to standard shape foam tips. T400 is the bore/center size. Tennmak has an improved version with a better foam and silicone like outer skin.
These are the different ones; T100, T200, T300 & T400:
Here's what they look like when cut shorter and used on some TWS. T200 size for the XM3 and T400 for the LP2s.
Unless you already have a good cutting tool, you can just mush them flat and use a razor blade
When I refer to APP tips, that means air pods pro replacement tips. I ordered some foam ones and removed the plastic center that mounts them to the oval shaped APP.
Once removed (peels off) they revert to round. They have a 4.5mm inner lip and 5.0mm bore, this is the small size:
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Also, there are now xelastec tips for the APP. I wonder if they can be de-cored and used on many TWS that need a short inner stem. Anyone try yet?