The reed that came with my new sop sax is a Rico Royal and it exactly fitted the aperture of the mouthpiece. It's just split, but fortunately I had another reed which is a Rillion. However, the Rillion reed is noticeably bigger than the Rico Royal - a bit wider and a lot longer. I want to get some more reeds tomorrow/today (Saturday) but does it make a difference (better or worse?) if the reed extends slightly beyond the width of the mouthpiece?

Personally I can't stand Rillion reeds. On sop saxes I use Hemke or Rico Royal, but it's really trial and error. I seem to recall that the sax mouthpiece that came with your sax is a slightly different shape and no reeds fit really well. Pupils of mine usually used rico royal tbh to begin with. I personally would upgrade to a yamaha 4C (or whatever suits you - 5C may be better) mouthpiece, as this will improve the soprano's sound immensely. I had a little girl that struggled with bottom C's and below on the sax you have, until she got a yamaha mouthpiece.

I've never heard of Rillion reeds - try it and see!

You'll have to go through the whole mp/reed/lig selection process at some stage anyway. If you're not sure how good the mp that came with the sax is I'd agree with Apassionata that a Yamaha 4c is a reliable and not too expensive option that could make an enormous difference.

As for the size of the reeds, there are whole threads on other fora devoted to people playing tenor reeds on alto saxes, bari reeds on tenors etc. They think it does something for the sound, I can't say I've ever tried it (though I remember having to use alto sax reeds on an alto clarinet once or twice in the dim and distant past, can't remember the relative dimensions). I'd suggest sticking with soprano sax reeds for now, but don't get too hung up on the size, especially if it's just a stop gap.

At Nottingham Sax Day we were given some new Rico Reeds to try. They are really good!! I know they are giving samples away so you might want ot look on the Rico website and ask for soem for your Sax. I think they are called Classic, they come in a foil bag wiht a little gel bag to keep them cool.

The new Rico reeds are Rico Reserve. They're "okay" in my opinion, better than the Rico Royal, but quite expensive.

Thanks for all the comments everyone. I've now got a batch of No 2 Rico Royals and I tried to get a mouthpiece but the shop didn't have one so I'll now order one online. The Yamaha site says this...

4C Easy to obtain a balanced, clear, and focused tone in any octave, ideal for professionals and beginners

5C Provides a somewhat richer tone with greater variety of colors than 4C and excellent flexibility and response. Popular with soloists

The 5C sounds like it would ultimately give a better tone, but is it still suitable for a beginner or would I be better to stick with the 4C?

I would go into your local music shop and try both if you can. For complete beginners I recommend the 4C, however oddly the Yamaha student plastic clarinet comes with a 6C (and I used to always have to swap them for 4C's in the shop!).

The Yamaha 4C has a narrower tip opening and so is easier to blow, plus you can generally use harder reeds with closer tip openings. If you can't try the mouthpieces and are an inexperienced wind player (sprry I can't remember!), then I would buy the 4C.

Have fun

That sounds safest. The shop I went to today didn't have Yamaha, so I'll contact netmusicalinstruments again after the Bank Holiday and hopefully I should get it on Wednesday. Thanks

Sounds good. Have fun trying them. They should make a huge difference.

I know a few people who've tried those (myself included) but no-one who likes them.