Firstly, place a measure where you wanna attach a pump.

Measure from the inside of the tube to the inside.

This time, it’s 53cm. “Inside to inside” length of a frame.

測ったらサイズ表と睨めっこ。

And then, check the sizing chart below.
【Compatible size】
M: 40 – 45cm
L: 45 – 50cm
XL: 49 – 54cm

So, Xl size works well for this bike.

It fits really well as you can see.

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XL size is compatible up to 54cm. Wait, what should we do if you’re taller or your frames is larger and it’s more than 54cm?

There is definitely some place shorter than the top tube on your bike.

When you attach a pump to the inside of rear triangle, please make sure it doesn’t get into the wheel with straps.

My recommendation is VOILE nano strap “9 inch”.

It’s same for the bike with a pump peg like PLATYPUS and ROMANCEUR.
Just measure from the inside to the inside where you wanna attach (in this picture, it’s about 41cm, so M would be the best.).

How about a frame pump with VOILE nano strap (9 inch) for your bikes?