Tabernacle of Testimony
“And after that I looked, and, behold, the temple of the tabernacle of the testimony in heaven was opened:” (Rev 15:5 KJV)
This is the Temple in Heaven that was seen in chapter 11:
“And the temple of God was opened in heaven, and there was seen in his temple the ark of his testament: and there were lightnings, and voices, and thunderings, and an earthquake, and great hail.” (Rev 11:19 KJV)
The Sea of Glass
“2 And I saw as it were a sea of glass mingled with fire: and them that had gotten the victory over the beast, and over his image, and over his mark, and over the number of his name, stand on the sea of glass, having the harps of God.
3 And they sing the song of Moses the servant of God, and the song of the Lamb, saying, Great and marvellous are thy works, Lord God Almighty; just and true are thy ways, thou King of saints.
4 Who shall not fear thee, O Lord, and glorify thy name? for thou only art holy: for all nations shall come and worship before thee; for thy judgments are made manifest.”
(Rev 15:2-4 KJV)