A Superior Court jury returned a verdict for the plaintiffs in their action to recover the principal amount of and interest and a "reasonable attorney’s fee” on a ninety-day promissory note in the *956principal amount of $6,396.38. 1. The defendant was barred by the parol evidence rule from introducing, in defense of the action, evidence of an alleged contemporaneous oral agreement between the parties to renew the note indefinitely until such time as the defendant could sell or refinance certain land. Such evidence would contradict the terms of the note, which was an unconditional promise to pay. See Commonwealth Trust Co. v. Coveney, 200 Mass. 379, 381 (1909); Buckley v. Hacking, 258 Mass. 525, 526 (1927); Sherman v. Koufman, 349 Mass. 606, 610 (1965); Trustees of Tufts College v. Parlane Sportswear Co., 4 Mass. App. Ct. 783, 783-784 (1976). The judge was correct in excluding the offered testimony. 2. There was sufficient evidence to support the jury’s award to the plaintiffs of $1,200 as a reasonable attorney’s fee. Expert opinion testimony regarding a reasonable fee was given by one of the plaintiffs, an attorney, and by the plaintiffs’ trial attorney. The former based his opinion on forty-eight years of experience at the bar, and the latter, on the Massachusetts Bar Association’s then existing guide to legal fees in retail collections. The jury were free to give the experts’ testimony such weight as they deemed appropriate and, on all the evidence, to determine a reason^ able fee. See Arena v. John P. Squire Co., 321 Mass. 423, 425-426 (1947); Perkins v. Blake, 3 Mass. App. Ct. 415, 418-419 (1975); Annot., 57 A.L.R. 3d 475, 489-540,502 n.71 (1974). Recovery was not limited to the amount sought by the plaintiffs in their declaration (complaint). See Goldstein v. Gontarz, 364 Mass. 800, 815-816, & n.15 (1974).
Philip D. Epstein for the defendant.
Anthony J. Turco & Barry Berkal, for the plaintiffs, submitted a brief.
Judgment affirmed.