A variable-length bit string is represented as BIT VARYING(n), where n is the maximum number of bits. If n is not specified, the length is set to 1,073,741,823 (maximum value).
CREATE TABLE bitvar_tbl(a1 BIT VARYING, a2 BIT VARYING(8));
INSERT INTO bitvar_tbl VALUES (B'1', B'1');
INSERT INTO bitvar_tbl VALUES (0b1010, 0b1010);
INSERT INTO bitvar_tbl VALUES (0xaa, 0xaa);
INSERT INTO bitvar_tbl(a1) VALUES (0xaaa);
SELECT * FROM bitvar_tbl;
a1 a2
============================================
X'8' X'8'
X'a' X'a'
X'aa' X'aa'
X'aaa' NULL
INSERT INTO bitvar_tbl(a2) VALUES (0xaaa);
ERROR: Data overflow coercing X'aaa' to type bit varying.