Plastic / delrin pellet inlet bolt housing for the following BSA air rifles:

R10
R10 MK2
R10 SE
RTen
Goldstar SE
Scorpion SE (all models)
Scorpion T-10
Ultra SE (all models)

.22 (5.5mm) Part number: 16-6787
.177 (4.5mm) Part number: 16-6835