NT-610XL-30Z  and other XL planers use a 30mm x 12mm x 2.5mm (don't get confused with the common 30x12x1.5, it will not work)  You need the 2.5mm thicknes.

The Northtech part # on the chinese made brand may be IC-251-230 

Price is for 1 single insert, some photos show a case of 6 for illustrative purposes only

Length =30mm

Width=12mm

Thickness=2.5mm***(Thicker than standard 30mm inserts)

Grade Kcr08

Holes 2 :   

Single knife for each 6 ordered, you get a free box

Sold in Boxes of 6

Made in Europe