Janome Hoop Frame Tension SPRING, Fits into the hoop screw and nut set (also sell)
Fits most:
200e, 300e, 350e, 9500, 9700, 10000, 10001, 11000, 11000SE
This is a Genuine Janome item
Will NOT fit 400E, 500E, MC9900, MC12000, MC14000, MC15000, MB-4