They're the aluminum front direct cups that have been first included in the TRF420 chassis kit. Lightweight aluminum components have a durable anodized finish.
Suitable Chassis TA07 MS*1, TA07 PRO*1, TRF419*1, TRF419X*1, TRF419XR*1 & TRF420 Chassis
*1Use with Item 51642 TRF420 Front Direct Pulley (37T). Two 3x10mm hex screws are individually required.
*The official Tamiya R/C Parts Matching List has numerous information about chassis suitable for Tamiya Spare and Hop-Up choice parts.