A thread protector for the receiver threads on your Silverback Airsoft SRS. This one has 14mm- threads so you can directly attach one of the SBA mussle brakes or another airsoft suppressor.
NOTE: Will not work with the Silverback gspec outer barrel. Will only work with the short outer barrel base found here....
https://www.shapeways.com/product/NNJQQ8Z64/srs-outer-barrel-base?optionId=96105294