I changed the English description.
Thank you 09 Lip!

Iron Spider Arm Extended inventory for compatibility with MOD. Please note that the number of stacks decreased instead.

Probably due to a bug in the game itself, when was wearing armor, found that the effect of the backpack's exercise capacity fluctuation has not come out. Even if you wear armor, there seems to be effects other than exercise capacity.

In order to increase the moving speed, it is necessary to take off all armor.

Instead it gained a little effect.