This 10x2.125" tube accommodates 6" rims with 10" tyres of width 2.125-2.5", such as:
10x2.125, the factory stock tyre on models of e-Glide & Mearth G120 & Mearth S Pro.
CST 10x2.5, which is a common stock tyre on T10-DDM (Zero 10X etc) and VDM-10 (Dragon Raptor etc).
It is also the Kaabo factory fitted tube on Mantis King GT running the CST 10x3.00-6 semi-off road tyre and likely the 10x3 and 80/65-6.5 road tyres. The shape of the valve is favourable for Mantis motors hubs as the bend retains the valve too be well protected adjacent to the hub.
Available in three bend types:
The 45& 90 degree variants are 104 grams, Superbsail branded with blue ring on underside and understood to be Xuancheng OEM.
The 90 degree is shown in product images.
Photo's of the 45 degree with brass colour valve are reflective of former inventory. The newer/current 45's have silver valve and similar length of the 90. The silver 45 is slightly shorter than the former brass 45 in images, but adopts identical valve shape / tilt etc.
The 0degree (shown in product image with generous length brass valve) is slightly heavier at 120 grams. Observed in non motor hubs on e-Glide and Mearth G120 and Mearth S Pro with the 10x2.125" tyre. When stocks exhausted these will progress to the Superbsail branded silver valve.
The Kaabo 90 degree factory tube by Xuancheng is branded XUAN CHENG 10x2/2.125. It is common for manufacturers to nameplate both 2 & 2.125 across these sizes.
Typically 90 degree is adopted on motor hubs to clear motor, 45 degree on non-motor hubs for swing arm clearance with the valve sitting between "the spokes of the wheel".
For 10x2.5 tyres, consider fitting this 10x2.5" sized tubes, it has a similar 90 degree tilt (bend shape).
Image below shows this 10x2.125" tube (on right) with two other similar size nameplate tubes. The 10x2 straight valve tube on the far left adopts similar size as this tyre and considered an equivalent with straight valve. The 10x2.125" straight valve tubeshown in center is designed for 6.6" rims such as the 10x2.125 tyre and . Tube nameplate and dimensions are not a conclusive method of determining appropriate fit relative to rim size and often 10x2/2.125" are not nameplated to inform appropriate rim size or compatible tyres. Choosing the appropriate tube is important for puncture resilience.
Xuancheng have a relatively small range of tubes, their catalogue Sept 2014: