Stem for tubeless tyres straight (no angle). Recommend replacing when renewing tyres.
Available in the common 17mm or the slightly longer 21mm, the later is understood to be appropriate for Apollo City Pro.
11mm seat for 8.8-9.5mm valve hole (although in practice on some hubs holes in this range may be too large, measure should be more towards the 8.8mm rather than 9.5mm).
Product images 5-7 show the 17mm valve contrasted against the longer TR438 valve as used on NAMI Electric models.
Most tubeless 11" makes/models use 12mm seat PVR50 valve which is a bent valve, with exceptions such as later model NAMI which adopts a 12.5mm seat straight TR438 valve. Use the TR438 valve as a straight valve in NAMI rather than this 11mm seat straight valve as it supports the wider 8.8-9.5mm hole adopted on NAMI motors. Same with Wolf Warrior and likewise in Dragon Hurricane.