Probably a stupid question, Will round handguard fit in a triangle handguard cap and vice versa?

Im only asking because I removed a round handguard cap and put a triangle one on, now im switching to a RAS or samco m44 and need a round handguard cap again....

Some of the early "round" handguards did work with a triangle front cap, but they were a little loose. A RAS will not work without a round cap.

The military M-16A2 round handguard was made to fit the older M-16A1 triangular front hand guard cap or the round cap. This was because the triangular handguard was made up of ONE left guard and ONE right guard. At one time, the supply of one of the sides reached zero and complete sets were not available in the supply system. The round guards came out so that one piece could fit either side and the locking nubs at the front could match either cap.