The Yuanxing 10x2.125" tube with straight valve suits models running Yuanxing 10x2.125" tyres (CY-344) in either 6.5" or 7" rim variety, including the Ninebot branded version of the 6.5" rim Yuanxing tyre (CY-327).
This Yuanxing tube is factory stock tube on makes/models of:
10x2.125 {-6.5} tyres on Ninebot FSeriessuch as F20, F25, F30, F40 & F65 and Ninebot D series such as D18, D28, D38.
Manufactured by Yuanxing with white nameplate marking YUAN XING, embossed with 102125-XX and blue line on underside.
Notes:
Image below shows this 10x2.125" straight valve tube (in centre) adjacent to two other tubes intended for smaller 6" rims: 10x2" straight (left) and 10x2.125" bent (right), measured at 4PSI. Counter-intuitively, this tyre has the smaller internal diameter despite being suited to the larger (6.5 and 7") rims. The other two are typically used on smaller 6" rims with higher profile tyres such as the wider 10x2.5" {-6} or lower pressure (36 PSI) 10x2.125" {-6}. The 10x2.125" {-7} tyre is relatively new, prior to this the 10x2.125 designation related exclusively to 6" rim for tyres such as the 10x2.125" {-6} or 10x2.125" {-6.5} tyres on Ninebot F/D series.. 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.
Often 10x2.5" tubeless tyres can be fitted in Ninebot F/D series negating need for tube.