Replacement collet nut.
Trend CE/CNS/635 1/4" Collet Extension Collet & Nut Set
Makita Router 1/4" Collet Nut for RP0900 / DRT50
Trend Router Collet Reduction Sleeve 10mm 8mm
Trend Router Collet Reduction Sleeve 8mm 6.35mm
Trend Router Collet Reduction Sleeve 6.35mm 3.2mm
Trend Router Collet Reduction Sleeve 12.7mm 9.5mm