They're the aluminum front side direct cups of first contained in the TRF420 framework kit. Lightweight aluminum elements have actually in fact 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 formal Tamiya R/C Parts Matching List has an abundance of details about framework appropriate Tamiya free and Hop-Up choice elements.